Coffee, Espresso & Brewing Equipment Glossary

This coffee glossary contains 634 coffee, espresso, brewing, roasting and equipment terms with practical definitions for home baristas, coffee roasters, café owners and anyone learning about coffee. Terms are listed alphabetically in simple, crawlable HTML. When Espresso Outlet publishes an in-depth article for a term, the term links directly to that published guide.

1

120V: Nominal North American low-voltage supply commonly used for home appliances and some commercial coffee equipment.

2

240V: A higher-voltage supply commonly used for commercial espresso machines and high-power equipment in North America. Exact plug, phase, and circuit requirements vary.

A

Acidity: The lively, tart, bright, or fruit-like sensory quality associated with organic acids and other compounds in coffee. Pleasant acidity is distinct from simply tasting sour.
Activated carbon: Porous carbon media used to adsorb chlorine, odors, and many organic compounds from water.
Actively heated group: A grouphead with a dedicated heater or temperature-control system used to stabilize or independently control group temperature.
Adjustment collar: A rotating collar or ring used to move one burr carrier and change grind size.
Aeration: Introducing air into milk during the early part of steaming, often called stretching.
Aerobic fermentation: Fermentation where coffee is exposed to oxygen during part or all of the fermentation period.
AeroPress: A compact manual brewer that steeps coffee in a chamber and uses a plunger to push the brew through a paper or metal filter.
Affogato: A dessert in which espresso is poured over gelato or ice cream.
Aftertaste: Flavor and tactile sensations that remain after coffee is swallowed or spit out.
Agitation: Movement of water and coffee grounds caused by pouring, stirring, swirling, pumping, bubbling, or other forces. It can change extraction rate and uniformity.
Agtron: A color-measurement system commonly used in coffee to quantify roast color using standardized instruments and scales.
Air gap: A physical separation between a drain outlet and wastewater receptor used to prevent backflow contamination, often required by plumbing code.
Airflow: The movement of air through a coffee roaster. It affects convection, smoke and chaff removal, combustion, and heat transfer.
Airpot: An insulated beverage dispenser with a pump mechanism used for serving batch-brewed coffee in commercial settings.
Alkalinity: Water's acid-neutralizing capacity, largely determined by bicarbonate in most brewing water. It buffers coffee acids and strongly affects perceived acidity.
Americano: Espresso diluted with hot water, usually producing a drink closer in strength to filter coffee while retaining espresso character.
Amperage: Electrical current, measured in amperes or amps. Circuit sizing must account for equipment current draw and applicable electrical codes.
Anaerobic fermentation: Fermentation conducted in a low-oxygen or oxygen-limited environment, often in sealed tanks. Producers may control time, temperature, pressure, or inoculation to influence flavor.
Arabica: Coffea arabica, a coffee species prized for broad flavor diversity and widely used in specialty coffee. It generally grows best at higher elevations and is more disease-sensitive than canephora.
Aroma: Volatile compounds perceived through smell, including aromas sensed directly from the brewed coffee and retronasally while tasting.
Astringency: A drying, puckering tactile sensation caused by compounds interacting with saliva; it is different from bitterness.
Astringent coffee: Coffee that leaves an unpleasant drying or puckering sensation, often associated with uneven or excessive extraction, excessive fines, channeling, or certain green-coffee characteristics.
Autofill valve: A valve controlled by the machine to admit water when a boiler level sensor calls for refill.
Automatic milk frother: A device that automatically draws, heats, and aerates milk without manual steam-wand technique.
Automatic tamper: An electric or pneumatic device that tamps a portafilter automatically to a repeatable force and depth.
Axial alignment: Alignment relating to whether the burr faces are parallel to each other across the grinding plane.

B

Backflushing: Cleaning a compatible espresso machine by placing a blind basket in the portafilter so pump pressure redirects water through the three-way valve and drain path.
Baked coffee: Coffee with flat, dull, bread-like or muted roast character often associated with insufficient roast momentum or prolonged low-energy roasting. The term is sensory rather than a perfectly defined physical condition.
Balance: The degree to which sweetness, acidity, bitterness, body, aroma, and flavor work harmoniously without one undesirable element dominating.
Barista lights: Integrated lights that illuminate the drip tray, cup, or extraction area on an espresso machine.
Batch brewer: An automatic commercial or home brewer that prepares multiple cups of filter coffee in one brewing cycle.
Bean bridging: Beans forming an arch or stable cluster above a grinder throat so they stop feeding even though the hopper is not empty.
Bean temperature: The temperature reported by the probe positioned to represent the coffee mass. It is a system measurement and not a perfect reading of every bean's internal temperature.
Bellows: A flexible air-pumping device fitted to some single-dose grinders to push air through the chamber and help expel retained grounds.
Bicarbonate: A common alkalinity-forming ion in water that buffers acids during coffee brewing.
Bimodal distribution: A particle-size distribution with two pronounced size populations or peaks, historically associated with many espresso grinding systems.
Bitter espresso: Espresso dominated by bitterness. Causes can include roast style, excessive extraction, high temperature, long contact, stale coffee, or an imbalanced recipe.
Bitterness: A basic taste sensation present naturally in coffee and often increased by darker roasting or certain extraction conditions.
Bleached filter: A paper filter whitened during manufacturing, commonly using oxygen-based or other modern bleaching processes.
Blending valve: A valve that mixes treated and untreated or differently treated water to achieve a target mineral concentration, hardness, or conductivity.
Blind basket: A portafilter basket with no holes, used to backflush compatible espresso machines and sometimes to measure pump pressure with appropriate equipment.
Blind cupping: Evaluating coffees without knowing their identities, origins, processing details, or other information that could bias judgment.
Blind shaker: A covered dosing cup or shaker used to mix and redistribute ground coffee before transferring it into the espresso basket.
Blonding: The visible lightening of espresso flow and crema later in a shot as the liquid becomes less concentrated.
Bloom: The initial pour in filter brewing that wets fresh grounds and allows trapped carbon dioxide to escape before the main pours.
Bloom ratio: The relationship between coffee dose and water used for the bloom, such as 1:2 or 1:3 coffee-to-bloom-water by mass.
Blooming espresso: A shot profile that introduces water, pauses or greatly reduces flow to allow the puck to saturate and swell, then resumes extraction.
Body: The perceived weight, thickness, richness, or physical presence of coffee in the mouth.
Body-focused burr: Informal terminology for burr geometry that tends to produce more texture, blended flavors, and traditional espresso body rather than maximum separation.
Boiler capacity: The internal volume of an espresso-machine boiler, normally stated in liters. Capacity influences thermal reserve but does not by itself determine recovery or performance.
Boiler inspection: A service check for scale, corrosion, leaks, probe condition, seals, and other internal boiler issues, normally performed by a qualified technician.
Boiler pressure: The steam pressure inside a service boiler, commonly used as a control variable for steaming temperature and power.
Bottomless portafilter: A portafilter with the underside removed so the basket bottom and espresso flow are visible, useful for diagnostics and cup clearance.
Boulders: Informal term for particles much larger than the target grind size in a particle-size distribution.
Bourbon: A major arabica variety and genetic family valued for cup quality and sweetness, with many mutations and selections used in coffee production.
Break the crust: The cupping step where the floating layer of grounds is disturbed with a spoon so aromatics can be evaluated and grounds can later be skimmed away.
Brew boiler: A boiler dedicated primarily to heating water used for espresso extraction.
Brew grinder: A grinder optimized primarily for filter and immersion brewing, often emphasizing clarity, low fines, broad coarse-range adjustment, and fast workflow.
Brew paddle: A paddle-style control used to start, stop, or modulate brewing. Depending on the machine it can be a simple switch or a true flow/pressure control.
Brew pressure: The pressure applied to the coffee bed during espresso extraction, typically discussed in bar. Actual puck pressure changes with flow and resistance.
Brew ratio: The relationship between coffee dose and water or beverage yield. The exact convention should be stated because filter brewing often compares coffee to brew water while espresso often compares dose to beverage mass.
Brew recovery: How quickly the brew system returns to its target temperature and operating state after an extraction.
Brew temperature: The temperature of water interacting with coffee during brewing. Actual temperature at the coffee can differ from a boiler or kettle set point.
Brew unit: The removable or internal mechanism in many superautomatic machines that doses, compresses, brews, and ejects the coffee puck.
Brew valve: A valve controlling water flow to the group during brewing. It may be mechanical, solenoid-operated, or integrated into a more complex hydraulic system.
Brew water: The water intentionally used to extract coffee, excluding or including bypass water depending on the brewing method and recipe.
Brushless motor: An electronically commutated motor without traditional carbon brushes, often used for efficient variable-speed grinder designs.
Bulk grinder: A high-capacity grinder intended to grind coffee into bags or containers for retail, batch brewing, cold brew, or production rather than directly into a portafilter.
Burr alignment: The condition in which opposing burr faces are positioned so the intended grinding surfaces are parallel and concentric enough for consistent operation.
Burr carrier: The structural component that holds and positions a grinder burr.
Burr chirp: The light metallic sound made when burr surfaces begin to touch while spinning, often used carefully to identify a grinder's mechanical zero.
Burr cleaning: Removing retained grounds and coffee oils from burrs, carriers, and the grinding chamber using brushing, vacuuming, appropriate cleaner, or disassembly.
Burr diameter: The nominal size of a burr set, usually measured in millimeters. Larger diameter can permit different geometry and throughput but does not automatically guarantee better grind quality.
Burr geometry: The shape and arrangement of burr teeth, cutting zones, angles, and surfaces that determine how beans are broken and strongly influence particle-size distribution.
Burr grinder: A grinder that crushes and cuts coffee between two shaped burr surfaces rather than chopping it with a spinning blade.
Burr life: The useful service interval of a burr set before grind quality, speed, heat, or consistency deteriorates enough to justify replacement.
Burr replacement: Installing a new burr set when existing burrs are worn, damaged, or being changed for a different grind or flavor performance.
Burr seasoning: Grinding a quantity of coffee through new burrs so sharp manufacturing edges and surfaces wear into a more stable operating condition. The amount needed varies greatly.
Burr set: The matched pair of burrs that performs the grinding work in a coffee grinder.
Burr wear: Gradual dulling, polishing, or dimensional change of burr cutting surfaces from use.
Bypass: Water that enters the final beverage without passing through the coffee bed, whether intentionally for dilution or unintentionally around a filter.

C

Caffè crema: A long espresso-style beverage, particularly associated with Swiss and central European traditions, produced at a much higher beverage yield than standard espresso.
Café au lait: Coffee served with hot or steamed milk, traditionally made with brewed coffee rather than espresso in French usage.
Café breve: An espresso drink made with steamed half-and-half or a cream-and-milk mixture instead of standard milk.
Café con leche: A coffee-and-milk drink found across Spanish-speaking cultures, with preparation varying from espresso-based versions to strong brewed coffee with hot milk.
Café cubano: A sweet Cuban-style espresso preparation in which sugar is traditionally whipped with early espresso to make a foamy sweet layer.
Calcium: A hardness-forming mineral ion that contributes to scale potential and can influence coffee extraction and flavor.
Calibrated tamper: A tamper designed to apply or indicate a repeatable force, travel, or spring setting.
Cappuccino: An espresso-and-milk drink traditionally smaller and foamier than a latte. Modern specialty versions commonly use espresso with textured milk in roughly 5–6 oz cups, though standards vary.
Carbon block: Compressed activated-carbon media with controlled pore structure, often combining chlorine reduction and particulate filtration.
Carbonate hardness: A hobbyist water term often used for hardness associated with bicarbonate/carbonate alkalinity. In coffee discussions it is frequently approximated with KH, although the chemistry is not identical in all cases.
Carbonic maceration: A fermentation approach inspired by winemaking in which intact or partially processed cherries ferment in a carbon-dioxide-rich environment. Coffee implementations vary widely.
Cartridge softener: A replaceable filter cartridge containing ion-exchange media to reduce hardness for coffee equipment.
Cascara: The dried skin and pulp of coffee cherries, sometimes brewed as a tea-like beverage. It is distinct from cascara sagrada.
Cast burr: A burr manufactured using a casting-based process rather than being entirely cut from bar or plate stock. The term is often used in discussions of specific SSP burr styles.
Castillo: A group of Colombian arabica cultivars developed for productivity, quality, and resistance to coffee leaf rust.
Catimor: A family of arabica cultivars derived from Caturra and Timor Hybrid genetics, often selected for coffee leaf rust resistance and productivity.
Catuai: An arabica hybrid developed from Mundo Novo and Caturra, valued for compact growth, productivity, and wide use in Latin America.
Caturra: A compact natural mutation of Bourbon that became important in Latin American coffee production because its shorter stature can support denser planting and easier harvest.
Center pour: Pouring mainly into the center of a coffee bed rather than tracing larger circles near the filter wall.
Cezve: A small long-handled pot used to prepare finely ground, unfiltered coffee in Turkish and related brewing traditions.
Chaff: The light papery material released from coffee during roasting, made largely from silverskin and other dry outer material.
Channeling: Preferential water flow through lower-resistance paths in a coffee bed or espresso puck, causing uneven extraction.
Charge temperature: The temperature reading at or just before green coffee is loaded into a roaster. The useful value depends on roaster design and probe placement.
Check valve: A one-way valve that allows fluid flow in one direction and blocks reverse flow.
Chemex: A glass pour-over brewer and carafe using proprietary thick paper filters, known for a clean cup and distinctive hourglass design.
Chloride: An ion that can occur naturally or from treatment; excessive chloride can contribute to corrosion risk in stainless-steel equipment.
Choked shot: An espresso extraction with extremely low or no flow because puck resistance is too high, commonly from grinding too fine, overdosing, or a blocked basket.
Circular pour: Pouring water in circular or spiral motions across the coffee bed to distribute water and agitation.
City roast: A traditional roast-degree term generally associated with a light-to-medium roast around or after first crack. Exact use varies by roaster.
Clarity: How distinctly individual flavors can be perceived without muddiness or excessive overlap.
Clarity-focused burr: Informal coffee-community terminology for a burr set that tends to emphasize flavor separation and transparency over heavy body.
Clever Dripper: A steep-and-release brewer that combines full-immersion steeping with a paper filter and a valve that opens when placed on a server.
Clogged chute: A grinder exit path blocked by compacted grounds, oils, static, or debris, causing poor dosing or backup into the burr chamber.
Cloth filter: A reusable woven filter that can provide a cup with more oils than paper and fewer particles than many metal filters, but requires careful cleaning and storage.
Clumping: Ground coffee sticking together in small aggregates, often from static, oils, fines, humidity, or chute compression.
Co-fermentation: A process in which coffee ferments with another biological material or culture, such as fruit, spices, or selected microorganisms. Practices and labeling vary widely.
Coated burr: A burr with a surface coating intended to change hardness, friction, corrosion resistance, appearance, or wear behavior.
Cocking the lever: Pulling a spring-lever machine's lever into the position that compresses the spring and fills or prepares the group for extraction.
Coffee: The brewed beverage made by extracting soluble flavor compounds from roasted seeds of coffee plants. In everyday use, the word can also refer to the roasted or green seeds themselves.
Coffee bean: The common name for the seed of the coffee cherry. It is not botanically a true bean.
Coffee bed: The layer of ground coffee through which water passes in methods such as pour-over, batch brewing, and espresso.
Coffee blend: A combination of two or more coffees selected to create a target flavor, cost, consistency, or brewing performance.
Coffee capsule: A sealed single-serve portion of ground coffee designed for a compatible capsule brewing system.
Coffee cherry: The fruit of the coffee plant. Each ripe cherry usually contains two seeds that become coffee beans after processing.
Coffee cooperative: An organization owned or governed by participating producers that may provide processing, marketing, financing, agronomy, or export services.
Coffee estate: A farm or agricultural property producing coffee, sometimes including its own processing infrastructure.
Coffee filter: A porous barrier that lets brewed liquid pass while retaining most coffee particles. Filters can be paper, cloth, metal, or other materials.
Coffee grinder: A machine or hand tool that breaks roasted coffee into particles of a controlled size for brewing.
Coffee lot: A defined quantity of coffee kept identifiable as one unit for processing, storage, sale, roasting, or quality evaluation.
Coffee pod: A broad term for pre-portioned coffee, which can mean soft paper pods such as ESE or rigid capsules depending on context.
Coffee processing: The set of steps used to remove fruit, dry the seed, and stabilize harvested coffee for storage and export. Processing strongly influences flavor and physical quality.
Coffee puck: The compact bed of ground coffee in an espresso basket before, during, or after extraction.
Coffee rest: The period roasted coffee is allowed to sit before brewing so degassing and flavor stabilization can progress. Appropriate rest varies with roast, brew method, and preference.
Coffee roaster: A machine designed to roast green coffee by applying and controlling heat while managing airflow, agitation, exhaust, and cooling.
Coffee roasting: The controlled application of heat to green coffee to create the chemical and physical changes that produce roasted-coffee aroma, flavor, color, brittleness, and solubility.
Coffee server: A vessel used to receive and serve brewed coffee, often placed beneath a dripper.
Coffee slurry: The mixture of coffee grounds and water present during immersion or percolation brewing.
Coffee terroir: The combined influence of location, climate, soil, elevation, variety, farming, and other environmental factors on a coffee's potential character.
Coffee urn: A large-capacity heated vessel used to brew, hold, or dispense coffee in food-service settings.
Coffee variety: A genetically distinct cultivated type within a coffee species, such as Bourbon, Typica, Caturra, or Gesha. In coffee, variety is usually more precise than the wine-derived term varietal.
Cold brew: Coffee extracted primarily with cool or room-temperature water over a relatively long contact time, usually by immersion or slow drip.
Cold start: Loading beans before starting the grinder, so the burrs begin turning with coffee already present.
Cold-brew concentrate: Cold brew prepared at high strength so it can be diluted with water or milk before serving.
Commercial espresso machine: An espresso machine engineered for café, restaurant, office, or other professional service, generally with higher capacity, duty cycle, serviceability, and utility requirements.
Commercial grinder: A grinder built for professional duty cycles, speed, serviceability, hopper capacity, or café workflow.
Commodity coffee: Coffee traded primarily as a standardized agricultural commodity, where price and volume generally matter more than traceable origin, lot separation, or distinctive cup quality.
Compact commercial espresso machine: A professional machine designed to reduce width, depth, power demand, boiler size, or group spacing while retaining commercial construction and workflow.
Complexity: The presence of multiple interesting, layered, or changing sensory impressions in a coffee.
Concentration gradient: A difference in dissolved-solids concentration between regions of the brewing system that helps drive diffusion and mass transfer.
Conduction: Heat transfer through direct contact, such as between coffee beans and a hot drum surface or between beans themselves.
Conductivity: A measure of water's ability to conduct electricity, which rises with dissolved ions and is often used to estimate TDS.
Cone brewer: A filter brewer with a conical coffee bed and filter geometry.
Conical burr: A burr set using an inner cone-shaped burr and an outer ring burr. Conical designs are common in hand grinders and many electric grinders.
Contact time: The period during which brewing water interacts with coffee grounds. In many methods it differs from total brew time.
Continuous pour: A pour-over technique that delivers most post-bloom water in one sustained pour.
Controlled fermentation: Fermentation in which producers deliberately manage variables such as time, temperature, oxygen, pH, vessel, microbial culture, or pressure.
Convection: Heat transfer through moving hot air or gas. It is a major heat-transfer mechanism in most coffee roasters.
Cool-touch steam wand: A steam wand designed with insulation or a tube-within-a-tube construction to reduce external surface temperature and milk burn-on.
Cooling flush: Running water through a heat-exchanger machine before brewing to remove overheated water and bring the group toward the desired brew condition.
Cooling tray: The perforated tray on many roasters where freshly dropped coffee is rapidly cooled by airflow and agitation.
Corrosion: Chemical or electrochemical deterioration of metal. Water chemistry, chlorides, oxygen, temperature, and mixed metals can all influence corrosion in coffee equipment.
Cortadito: A Cuban espresso drink combining sweetened café cubano with a small amount of steamed or heated milk.
Cortado: A small drink combining espresso with a roughly similar amount of warm textured milk, designed to soften espresso intensity while staying coffee-forward.
Crema: The foam-like layer on espresso formed from emulsified oils, suspended material, surfactants, and carbon dioxide released under pressure.
Cup warmer: The top surface or dedicated tray used to preheat cups using passive machine heat or an active heating element.
Cupping: A standardized or semi-standardized method of evaluating coffee by steeping measured grounds in bowls or cups, breaking the crust, and tasting with spoons.
Cupping bowl: A cup or bowl of standardized or consistent size used to prepare coffee for cupping evaluation.
Cupping score: A numerical quality score assigned during a structured coffee evaluation. The exact protocol and score meaning depend on the system used.
Cupping spoon: A deep, round spoon designed for coffee cupping, allowing tasters to collect and slurp a controlled amount of brew.
Cups per hour: A rough capacity metric estimating how many beverages a machine or brewing system can produce in an hour. Real output depends heavily on drink mix and workflow.
Cyclone: A device that uses centrifugal airflow to separate chaff and particulate matter from roaster exhaust.

D

Dark roast: Coffee roasted to a relatively advanced degree, typically with increased roast-derived bitterness, smoke, lower perceived acidity, and often visible oils at sufficiently dark levels.
Decaf coffee: Coffee from which most caffeine has been removed before roasting using a decaffeination process such as water, solvent, or supercritical carbon dioxide processing.
Declining-pressure profile: A shot profile where pressure gradually falls later in extraction, mimicking or adapting concepts from spring-lever machines.
Declumper: A flap, screen, or flexible element at a grinder's exit designed to break up clumps and influence grounds flow.
Dedicated circuit: An electrical branch circuit reserved for one appliance or specified group of equipment to provide sufficient capacity and reduce nuisance tripping.
Degassing: The release of gases, especially carbon dioxide, from roasted coffee after roasting. Degassing rate affects packaging and brewing behavior.
Density sorting: Separating coffee by density using equipment or water-based methods to remove light, immature, damaged, or otherwise undesirable seeds.
Depulping: Mechanically removing the outer skin and much of the fruit pulp from coffee cherries before fermentation or drying.
Descaling: Chemically dissolving mineral scale from equipment. It should only be done when appropriate for the machine design and manufacturer instructions.
Detergent backflush: Backflushing with a manufacturer-approved espresso-machine cleaning detergent to dissolve coffee oils in the group and valve path.
Development phase: The portion of the roast after first crack begins and before the coffee is dropped or cooling begins. How it is managed influences roast character and solubility.
Development time ratio: The percentage of total roast time spent after the chosen first-crack reference point. It is a descriptive metric, not a universal recipe for quality.
Dialing in: Adjusting grind size and, when needed, dose, yield, temperature, pressure, or other variables until the coffee reaches the desired flavor and flow.
Diffusion: The movement of dissolved compounds from regions of higher concentration toward lower concentration, one mechanism involved in coffee extraction.
Direct lever: A lever espresso design where the barista's force directly controls the piston and therefore brew pressure throughout the shot.
Direct plumb: An equipment configuration connected to a building's pressurized water supply rather than relying only on an internal reservoir.
Direct trade: A broad, non-regulated term for sourcing relationships in which a roaster or buyer works more directly with producers or origin partners than in conventional commodity channels.
Direct-fired roaster: A roasting design in which burner heat or flame has a relatively direct thermal relationship with the roasting chamber or drum.
Dispersion plate: A plate, block, or diffuser above the shower screen that helps distribute incoming brew water across the group.
Dissolution: The process by which soluble coffee compounds move into and become molecularly dispersed in brewing water.
Distribution: Arranging grounds evenly throughout an espresso basket before tamping to reduce density differences and channeling.
DLC burr: A burr coated with diamond-like carbon, a hard low-friction coating used to improve wear resistance and change surface properties.
Donut extraction: A bottomless-portafilter pattern where flow appears mainly around the basket perimeter while the center remains comparatively dry or slow.
Dose: The mass of dry coffee used for a brew or espresso shot, usually measured in grams.
Dose drift: A gradual change in delivered ground-coffee mass from a timed or volumetric grinder because of bean level, grind setting, humidity, burr wear, or feed behavior.
Doser grinder: A grinder that accumulates ground coffee in a dosing chamber and dispenses portions mechanically.
Dosing cup: A small cup used to catch a grinder dose and transfer grounds into a portafilter or brewer.
Dosing funnel: A ring or collar fitted to the espresso basket or portafilter to reduce spills and provide room for WDT or shaking.
Double espresso: An espresso prepared as a double serving, commonly using a double basket and modern doses around the high teens to low twenties of grams, depending on basket and recipe.
Drain box: A connection or collection point beneath or behind commercial coffee equipment that receives wastewater from drip trays or other drains.
Drain line: The hose or pipe carrying wastewater from a machine, drip tray, pitcher rinser, or sink to a drain.
Drawdown: The period when water drains through the coffee bed and filter, especially toward the end of pour-over brewing.
Drip coffee: Coffee brewed by allowing hot water to pass through a bed of grounds and a filter, either manually or with an automatic brewer.
Drip stop: A valve that prevents brewed coffee from dripping when the carafe or server is removed or when a brew basket is closed.
Drip tray: The removable or plumbed tray beneath an espresso machine's group and steam area that catches water, spills, and purge liquid.
Drop temperature: The temperature reading when roasted coffee leaves the roasting chamber and enters cooling. Values are roaster- and probe-specific.
Drum roaster: A roaster that tumbles coffee in a rotating drum while heat is transferred through hot air, drum surfaces, and radiation.
Drum speed: The rotational speed of a drum roaster. It influences bean movement, contact, mixing, and the way heat is distributed.
Dry mill: A facility that prepares dried parchment or natural coffee for export by hulling, cleaning, sorting, grading, and bagging.
Dry steam: Steam with relatively little entrained liquid water, generally preferred for fast milk texturing with less dilution.
Drying phase: The early portion of roasting during which beans lose substantial free moisture and progress toward yellowing.
Dual boiler: An espresso machine with separate boilers for brew water and steam, allowing independent temperature control and simultaneous brewing and steaming.
Duty cycle: The amount and pattern of operation equipment can sustain before it must rest or risks overheating. Commercial grinders and machines are designed for heavier duty cycles.
Dynamic pressure: Pressure measured while fluid is flowing through the system and resistance is present.

E

E61 cam lubrication: Applying a small amount of appropriate food-safe lubricant to the E61 group cam and related sliding surfaces during service to reduce wear and lever stiffness.
E61 grouphead: A classic heavy chrome-plated brass group design introduced by Faema in 1961, known for a thermosiphon-heated group, mechanical brew lever, and pre-infusion chamber.
Eco mode: A power-saving state that lowers temperature, disables heaters, or otherwise reduces energy use after a period of inactivity.
Economizer: A mixing or temperature-control device on some commercial machines that tempers very hot boiler water with cooler water before dispensing from the hot-water outlet.
Edge channeling: Preferential espresso flow along the basket wall, often associated with poor edge distribution, basket geometry, puck shrinkage, or damage.
Elevation: The altitude at which coffee is grown. Higher elevation often slows cherry maturation and can support greater density and flavor complexity, but elevation alone does not determine quality.
Endgame grinder: Coffee-community slang for a grinder someone expects to keep long-term without feeling a need to upgrade; the meaning is entirely personal and budget-dependent.
Environmental temperature: A roaster temperature measurement intended to represent the hot environment around the coffee, with exact meaning depending on roaster and probe location.
ESE pod: Easy Serving Espresso: a standardized paper pod containing a pre-measured dose of espresso-ground coffee for compatible machines.
Espresso: A concentrated coffee beverage produced by forcing hot water through a compact bed of finely ground coffee under pressure. Modern recipes vary widely in dose, ratio, pressure, flow, and time.
Espresso blend: A coffee blend designed or marketed with espresso brewing in mind. It may emphasize body, sweetness, crema, balance with milk, or consistency, but any suitable coffee can be brewed as espresso.
Espresso grinder: A grinder capable of making fine, consistent adjustments in the espresso range and producing grounds with suitable particle distribution and repeatability.
Espresso macchiato: Espresso 'marked' with a small amount of milk or foam. It is much smaller and more coffee-forward than the large caramel-style drinks sometimes sold under the macchiato name.
Espresso machine: Equipment that heats water and delivers it through a prepared coffee puck under controlled pressure to make espresso, often with a steam system for milk drinks.
Espresso machine detergent: A cleaning chemical formulated to remove coffee oils and residue from groupheads, baskets, portafilters, and compatible brew circuits.
Espresso paper filter: A paper disc used above or below the espresso puck. Bottom papers can alter flow and reduce fines migration; top papers can help keep the group clean.
Espresso ratio: The relationship between dry coffee dose and liquid espresso yield by mass, such as 18 g in and 36 g out for a 1:2 ratio.
Espresso roast: A roast profile developed with espresso extraction in mind. It may be more soluble or developed than a filter roast, although the term does not require a particular darkness.
Espresso shot: A single brewing cycle of espresso, whether it is split between cups or served as one beverage.
Espresso station: The organized workspace containing an espresso machine, grinder, scale, tamping tools, knock box, milk pitchers, and other accessories.
Espresso tonic: A cold drink combining espresso with tonic water, often served over ice.
Etching: Adding latte-art details by drawing through foam or crema with a pointed tool after pouring.
ETL certification: A safety certification mark from Intertek indicating a product has been tested to applicable North American standards.
Even extraction: Extraction in which water interacts relatively uniformly with the coffee bed or puck, reducing areas that are much more or less extracted than others.
Excelsa: A coffee type historically treated as a separate species but commonly classified within Coffea liberica; it is grown in limited regions and can contribute unusual fruit and tart characteristics.
Exchange retention: The amount of old coffee exchanged with or released into a new dose during normal grinding, a more workflow-relevant measure than total hidden retention in many grinders.
Expansion valve: A pressure-relief component that opens at a set pressure to protect or regulate portions of an espresso machine's hydraulic circuit.
Extended fermentation: A fermentation held longer than a producer's conventional process in an effort to create particular flavor or processing effects.
Extraction: The transfer of soluble and suspended coffee compounds from grounds into water during brewing.
Extraction yield: The percentage of the dry coffee dose that ends up dissolved in the brewed beverage, commonly estimated from beverage mass and TDS.

F

Facing: A roast defect characterized by a broad scorched patch on one side of a bean, usually related to excessive hot-surface contact.
Fair Trade: Coffee certified under a fair-trade standard that includes requirements related to producer organizations, trading practices, and minimum or premium payments. Specific rules depend on the certifying organization.
Fast shot: An espresso extraction that reaches the target yield too quickly for the intended recipe, usually requiring a finer grind or another resistance adjustment after puck-prep issues are ruled out.
Fellini move: A lever-machine technique involving partial lever movements to refill or manipulate the group before extraction; it is machine-specific and should be used only where appropriate.
Fermentation tank: A vessel used to hold coffee during fermentation, often made of concrete, tile, stainless steel, plastic, or other food-safe material.
Fill probe: A conductive or other level sensor used to detect boiler water level so an autofill circuit can add water when needed.
Filter basket: The perforated metal insert in a portafilter that holds the ground coffee during espresso brewing.
Filter capacity: The amount of water or contaminant load a treatment cartridge can handle before replacement, often specified in gallons, liters, grains, or months.
Filter head: The fixed housing or connection component into which a replaceable water-filter cartridge locks.
Filter replacement interval: The scheduled time or water-volume limit for replacing a water-treatment cartridge before capacity, flow, or protection becomes inadequate.
Filter rinse: Rinsing a paper or cloth filter with water before brewing to remove loose fibers or paper taste and preheat the brewer.
Filter roast: A roast profile developed primarily for filter brewing, often with enough development for sweetness and solubility while preserving clarity and origin character.
Filtration manifold: A mounted assembly that holds one or more water-treatment heads, cartridges, valves, gauges, or blending components.
Fines: The smallest particles in a grind distribution. Fines extract quickly, migrate through coffee beds, and can increase resistance or astringency when excessive.
Finishing teeth: The later cutting features on a burr that refine particles toward the target size before grounds exit the burr set.
First crack: An audible stage of roasting when internal pressure causes beans to expand and fracture, producing popping sounds and marking a major structural transition.
First drip: The moment the first visible espresso reaches the cup or exits the basket, sometimes used as the starting reference for shot timing.
Flash brew: Hot-brewed filter coffee made directly over ice so extraction occurs hot and the beverage is rapidly chilled and diluted to the target strength.
Flat burr: A burr set using two generally flat, ring-shaped cutting discs facing each other. Flat-burr grinders can be designed for many different particle distributions and flavor styles.
Flat white: An espresso-and-textured-milk drink generally smaller and more coffee-forward than a latte, with a thin integrated microfoam layer. Definitions vary by café and region.
Flat-bottom brewer: A pour-over or automatic brew basket with a relatively flat coffee-bed geometry rather than a pointed cone.
Flavor note: A descriptive comparison used to communicate a sensory impression, such as blueberry, cocoa, jasmine, or caramel. It does not normally mean those ingredients were added.
Flavor wheel: A structured visual vocabulary used to organize and communicate coffee aroma and flavor descriptors, such as the SCA Coffee Taster's Flavor Wheel.
Floor drain: A drain set into the floor, often used for commercial equipment, sinks, or water-treatment discharge.
Flow control: A mechanism or control strategy that lets the barista restrict or vary brew-water flow, often using a needle valve or electronically controlled pump.
Flow profiling: Deliberately changing water flow rate during espresso extraction, with puck pressure responding to the relationship between flow and puck resistance.
Flow rate: The amount of water or beverage moving through a system per unit of time, commonly expressed in grams or milliliters per second.
Flowmeter: A sensor that measures water movement, commonly used by volumetric espresso machines to stop shots after a programmed pulse count.
Fluid-bed roaster: A roaster that suspends and agitates beans primarily with a stream of hot air rather than a rotating drum.
Flush group: Running water through an espresso group without a portafilter to clear loose grounds, stabilize temperature on some machines, or rinse the shower screen.
Flush-and-wait: A heat-exchanger temperature-management technique that uses a deliberate flush followed by a short recovery wait before brewing.
Food-safe lubricant: A lubricant approved for incidental food-contact environments and appropriate for specific moving components such as E61 cams or seals.
Fragrance: In coffee evaluation, the aromatic impression of dry ground coffee before water is added, though the term is sometimes used more broadly.
Free pouring: Creating latte art entirely by controlling milk flow from the pitcher rather than drawing on the surface with a tool.
French press: An immersion brewer where coarse-ground coffee steeps in a vessel and a mesh plunger separates most grounds before pouring.
French roast: A traditional term for a dark roast taken well into roast-derived flavors, commonly near or into second crack.
Full City roast: A traditional roast-degree term generally darker than City roast and before or near the beginning of second crack. Definitions vary.

G

Gear pump: A positive-displacement pump that moves water between meshing gears and can support precise variable-flow or pressure-control systems in advanced espresso machines.
General hardness: A brewing-water term for total calcium and magnesium hardness, often abbreviated GH.
Gesha: An arabica variety or family associated with exceptional floral, citrus, tea-like, and aromatic cup profiles when grown and processed well. The spelling Geisha is also common.
GFCI: Ground-fault circuit interrupter protection that quickly disconnects power when leakage current suggests a shock hazard. Requirements depend on local electrical code.
Ghost burr: A distinctive toothed burr geometry, especially associated with some brew-focused grinders, that breaks beans with protruding teeth rather than conventional flat-burr cutting patterns.
Gibraltar: A name popularized for a cortado-like espresso-and-milk drink served in a specific small Gibraltar glass; usage varies by café.
Gigleur: A small calibrated restrictor or jet in an espresso-machine hydraulic circuit used to limit flow and influence pressure or pre-infusion behavior.
God shot: Coffee-community slang for an exceptionally delicious espresso shot that seems unusually well balanced or memorable.
Gooseneck kettle: A kettle with a narrow curved spout designed for controlled pouring speed and placement in manual brewing.
Gravimetric espresso: Espresso dosing controlled by beverage mass measured with an integrated scale, allowing the machine to stop at a target weight.
Gravity drain: A drain system that relies on downward slope rather than a pump, so correct hose routing and elevation are essential.
Green coffee: Unroasted coffee seeds after processing and drying. Roasters buy green coffee and transform it through heat into roasted coffee.
Grind adjustment: The mechanism used to change the distance or relationship between burrs and therefore grind size.
Grind drift: A gradual unintended change in effective grind setting or shot behavior caused by adjustment movement, heat, burr wear, mechanical play, bean changes, or environmental conditions.
Grind speed: The rate at which a grinder processes coffee, often expressed in grams per second. It depends on burrs, motor, RPM, grind size, and coffee.
Grind uniformity: How narrowly particles cluster around the desired size. Uniformity is only one dimension of grinder performance and does not automatically determine cup quality.
Grind-by-weight: A grinder that uses an integrated scale or load cell to stop grinding when a target ground-coffee mass is reached.
Grinder cleaner: A food-safe cleaning product designed to pass through burr grinders and absorb or dislodge oils and residue without disassembling the grinder.
Grinder jam: A condition where burrs or feed path cannot rotate or pass coffee because of a foreign object, compacted grounds, an excessively fine setting, or another blockage.
Grinder RPM: The rotational speed of a grinder's driven burr or burr carrier, measured in revolutions per minute.
Grinder-first upgrade: The common recommendation to improve grinder quality before upgrading the espresso machine when grind consistency and adjustment are the current limiting factors.
Grinding chamber: The internal area around the burrs where beans are broken into ground coffee.
Grounds chute: The passage that directs ground coffee from the burr chamber into a portafilter, dosing cup, bin, or bag.
Group gasket: The sealing gasket between the grouphead and portafilter that prevents water from leaking around the portafilter during brewing.
Group-gasket replacement: Replacing the portafilter sealing gasket after it hardens, cracks, leaks, or reaches a scheduled service interval.
Grouphead: The espresso-machine assembly that distributes brew water to the portafilter and coffee puck.
Grouphead pressure gauge: A gauge located at or near the group to display brew pressure closer to the coffee puck than a pump-mounted gauge.
Gusher: An espresso shot that flows far too quickly with too little resistance, usually associated with a grind that is too coarse, insufficient dose, severe channeling, or poor puck integrity.

H

Half-caf: A blend containing roughly equal portions of caffeinated and decaffeinated coffee, used to reduce caffeine while retaining some of the character of regular coffee.
Hand grinder: A manually powered coffee grinder turned by a crank, commonly using conical burrs.
Hardened-steel burr: A steel burr heat-treated or otherwise hardened for wear resistance and cutting durability.
Hardness breakthrough: The point where a softening or treatment cartridge becomes exhausted enough that hardness begins passing through at increasing levels.
Hario Switch: A V60-style brewer with a valve that can hold water for immersion and release it for percolation or hybrid recipes.
Headspace: The gap between the tamped coffee puck and the shower screen or dispersion assembly before brewing.
Heart: A foundational latte-art design made by establishing a white circle and drawing through it to form a heart shape.
Heat exchanger: An espresso-machine system in which brew water passes through a tube or chamber heated by a larger steam boiler, allowing brewing and steaming at the same time.
Heating element: An electrical resistance heater that converts electricity into heat for a boiler, thermoblock, group, or other machine component.
Hertz: Cycles per second of alternating-current frequency. North American equipment commonly uses 60 Hz while many other regions use 50 Hz.
High brew pressure: Brew pressure above the intended range, potentially caused by pump or OPV adjustment, excessive puck resistance, a blockage, or gauge error.
High-and-dry grounds: Grounds left attached high on a filter wall after pouring, potentially indicating strong agitation, wall pours, or an unevenly settled bed.
High-flow basket: A basket designed to offer relatively low hydraulic resistance or higher potential flow, often requiring finer grinding or recipe changes.
High-uniformity burr: A term commonly used for burr geometry designed to produce a relatively narrow particle distribution, often associated with high-clarity espresso.
Hollow coffee: A sensory description for coffee that seems to lack sweetness, middle-palate flavor, or satisfying structure despite having acidity or bitterness.
Home barista: A coffee enthusiast who prepares espresso or other specialty coffee at home using barista-style equipment and techniques.
Home espresso machine: An espresso machine designed primarily for residential use, typically with lower duty-cycle and utility requirements than commercial equipment.
Honey process: A process in which coffee is pulped but some mucilage remains on the parchment during drying. Terms such as yellow, red, and black honey often describe different handling approaches.
Hopper grinder: A grinder designed to hold a supply of beans in a hopper and dose from that supply over multiple grinding cycles.
Hot start: Starting the grinder motor before beans are fed into the burrs, often used in single-dose workflows to reduce startup load or alter feeding behavior.
Hot-water tap: An espresso-machine outlet that dispenses hot water for tea, Americanos, rinsing, or other service uses.
Hot-water tower: A commercial appliance dedicated to storing and dispensing hot water for tea, manual brewing, or food service.
Hulling: Mechanical removal of dried parchment from washed coffees or dried fruit layers from natural coffees before final sorting.
Hybrid brewer: A brewer combining immersion and percolation behavior, often by steeping with a closed valve before releasing the brew through a filter.

I

Immersion brewing: A method where coffee grounds steep in the full volume of brew water before separation, as in a French press or cupping.
Indirect-fired roaster: A roasting system that heats air or another surface before that heat reaches the coffee, reducing direct flame influence.
Insolubles: Coffee material suspended in the beverage rather than dissolved, including fine particles and oils. Filtration method strongly affects their amount.
Ion exchange: A water-treatment process that swaps dissolved ions using resin, such as exchanging calcium and magnesium for sodium or hydrogen.
Ionizer: A device that generates ions to neutralize static charge in ground coffee as it exits a grinder.
Italian roast: A traditional term for a very dark roast. There is no universal industry standard for the exact degree.

J

No glossary terms currently begin with J.

K

Kalita Wave: A flat-bottom pour-over brewer using wave-shaped filters and multiple small drain holes.
Kilowatt: A unit of power equal to 1,000 watts, commonly used to describe large heating loads.
Kyoto-style coffee: A slow-drip cold-brewing method where cold water drips gradually through a coffee bed, often using a tall multi-chamber tower.

L

Latte: An espresso drink with a relatively large proportion of steamed milk and a thin layer of microfoam.
Latte art: Patterns formed by controlling the flow of textured milk into espresso so white microfoam and brown crema create contrasting designs.
Latte-art pitcher: A milk pitcher selected for spout shape, size, balance, and control when pouring latte art.
Lever espresso machine: An espresso machine that uses a lever-driven piston to create brew pressure, either directly by the barista or through a compressed spring.
Lever profile: The naturally or deliberately changing pressure pattern of a lever espresso shot, often high after spring release and declining as the piston travels.
Liberica: Coffea liberica, a less widely cultivated coffee species known for large cherries and distinctive flavor characteristics.
Light roast: Coffee roasted to a relatively light degree, generally emphasizing origin character, acidity, and aromatic complexity while maintaining lower roast-derived flavor.
Limescale: Hard mineral deposits, primarily calcium carbonate, that form when mineral-rich water is heated or concentrated.
Line pressure: The pressure present in the building water supply feeding plumbed equipment.
Line-pressure pre-infusion: Pre-infusion that uses incoming mains-water pressure before the pump raises brew pressure, common in certain plumbed rotary-pump machines.
Long black: A drink made by pouring espresso over hot water, commonly associated with Australia and New Zealand; the order of assembly helps preserve surface crema.
Low brew pressure: Brew pressure below the intended operating range, potentially caused by low puck resistance, pump setting, pump wear, leaks, water supply, or a faulty gauge.
Low flow: Reduced water debit from a group or brewer, often associated with scale, clogged jets or screens, restricted filters, weak pumps, or low supply pressure.
Lungo: A longer espresso with a higher beverage yield relative to dose than a normale, typically producing a more diluted shot with greater total extraction.

M

Macro adjustment: A larger grind-setting change used to move quickly between broad grind ranges.
Macrofoam: Milk foam with larger, more visible bubbles and a drier, less integrated texture than microfoam.
Magnesium: A hardness-forming mineral ion that can contribute strongly to extraction and flavor while generally forming different scale behavior than calcium.
Maillard reaction: A group of heat-driven reactions between amino compounds and reducing sugars that contribute substantially to browning, aroma, and flavor development during roasting.
Manual espresso machine: An espresso machine where the user directly supplies or controls brewing force or flow, often with a lever rather than an electric brew pump.
Maragogipe: A large-bean mutation of Typica sometimes called elephant bean coffee and used as a parent of Pacamara.
Marker test: A burr-alignment check where removable marker is applied to a burr face and the burrs are brought into light contact; the wipe pattern indicates relative contact.
Mechanical dryer: Equipment that uses heated or forced air and tumbling or other movement to reduce coffee moisture under controlled conditions.
Mechanical pre-infusion: Pre-infusion created by springs, chambers, valves, or group geometry rather than a fully electronic control algorithm.
Medium roast: A broad roast range balancing origin character with more developed caramelized and roast-derived flavors.
Metal filter: A reusable perforated or mesh filter that allows more oils and fine particles into the beverage than most paper filters.
Micro adjustment: A small grind-setting change used for precise dialing in, particularly for espresso.
Micro-channeling: Small localized flow paths through an espresso puck that may not produce dramatic visible sprays but can still make extraction less even.
Microfoam: Glossy steamed milk containing very small, evenly distributed bubbles that create a smooth texture and support latte art.
Microlot: A relatively small, separately traceable lot of coffee kept distinct because of producer, plot, variety, processing, quality, or flavor.
Micrometric adjustment: A fine, continuously variable grinder adjustment mechanism designed to permit very small burr-spacing changes, particularly useful for espresso.
Milk carafe: A removable milk container used by many superautomatic machines to store milk and feed an automated frothing system.
Milk pitcher: A metal jug used to steam and pour milk for espresso drinks.
Milk steaming: Using steam to heat milk while incorporating controlled air and creating a stable texture suitable for espresso drinks.
Milk stone: A hardened deposit of milk proteins, minerals, and fats that can build up on steam and dairy-contact equipment.
Milk texturing: Developing the desired bubble size, viscosity, sheen, and temperature in milk with steam.
Milk-system cleaner: A detergent formulated to dissolve milk proteins and fats from steam, frothing, or automatic milk systems.
Mise en place: The practice of arranging tools, ingredients, cups, towels, and workflow before service so a barista can work efficiently and consistently.
Mocha: An espresso-and-milk drink flavored with chocolate, often finished similarly to a latte.
Moisture content: The percentage of water in green or roasted coffee by mass. Green coffee moisture is monitored because excessive or insufficient moisture can affect storage and roasting.
Moka pot: A stovetop brewer that uses steam pressure to push hot water from a lower chamber through coffee into an upper chamber. It does not brew at true espresso pressure.
Motor stall: A grinder motor stopping or failing to accelerate under load because torque demand exceeds available motor output or protection activates.
Mouthfeel: The complete tactile sensation of coffee in the mouth, including body, viscosity, creaminess, dryness, astringency, and texture.
Mucilage: The sticky, sugar-rich layer surrounding the coffee parchment inside the fruit, important in fermentation and honey-process coffees.
Muddy cup: Coffee with low flavor separation and a heavy or silty impression, often associated with fines, metal filtration, over-agitation, grinder characteristics, or roast style.
Multi-boiler: A machine with multiple independently controlled boilers, commonly one steam boiler plus separate brew boilers for groups.
Multipurpose burr: A burr geometry intended to perform well across espresso and filter ranges rather than being optimized for only one brewing style.
Mundo Novo: An arabica cultivar derived from a natural cross of Bourbon and Typica-related material, known for vigor and productivity.

N

Nanolot: An especially small, highly separated coffee lot, often representing a tiny harvest, experimental process, or exceptional selection.
Natural process: A process in which intact coffee cherries are dried before the dried fruit layers are mechanically removed.
Needle valve: A finely adjustable valve using a tapered needle to control fluid flow through a small opening, commonly used in manual flow-control devices.
NEMA plug: A plug configuration standardized by the National Electrical Manufacturers Association in North America, identified by codes such as 5-15, 5-20, 6-20, or L6-30.
New crop coffee: Coffee from the most recent harvest season for its origin, generally contrasted with older stored crop.
No flow: A condition where brew water does not exit the group. Possible causes range from an empty reservoir and closed water valve to pump, solenoid, scale, blockage, or control faults.
Normale: A conventional espresso ratio between ristretto and lungo, often near 1:2 dose-to-yield in modern specialty practice.
NSF certification: Certification indicating that equipment has been evaluated to applicable NSF sanitation and food-equipment standards. The exact standard should be confirmed for each product.
NTC thermistor: A temperature sensor whose electrical resistance decreases as temperature increases, commonly used in coffee equipment.

O

Omni roast: A roast profile intended to work across more than one brewing style, often both espresso and filter, rather than being optimized narrowly for a single method.
On-demand grinder: A grinder that grinds fresh coffee directly for each order, usually by time, weight, or manual activation rather than dosing from a pre-ground chamber.
One-group espresso machine: A commercial or prosumer espresso machine with one brew group, suited to lower-volume service, mobile setups, restaurants, or cafés with limited bar space.
Optical sorting: Machine sorting that uses cameras or sensors to identify and reject coffee by color or other visible characteristics.
Organic coffee: Coffee produced and certified under an organic standard that restricts specified synthetic inputs and requires documented agricultural and handling practices.
Origami dripper: A ribbed cone brewer from Japan designed for paper filters and flexible flow characteristics.
Over-extraction: A condition where extraction has progressed beyond the desirable balance for the coffee and recipe, sometimes producing dryness, harsh bitterness, or astringency.
Overpressure valve: A valve used in many pump systems to limit brew-circuit pressure by diverting excess flow when pressure exceeds its setting.

P

Pacamara: A large-bean arabica hybrid of Pacas and Maragogipe, especially associated with El Salvador and known for potentially complex, distinctive cups.
Paper filter: A disposable cellulose coffee filter that removes most visible grounds and a substantial portion of oils and fine particles.
Parchment coffee: Dried coffee seed still enclosed in the papery parchment layer that remains after wet processing and before dry milling.
Particle-size distribution: The range and relative proportion of particle sizes produced by a grinder, usually abbreviated PSD.
Past crop coffee: Coffee held from a previous harvest season. Quality can remain good with proper storage, but green coffee changes over time.
Patio drying: Drying coffee on a paved patio or similar flat surface where the coffee is spread and regularly turned.
Peaberry: A coffee seed that develops as a single rounded seed inside a cherry instead of the more common pair of flat-sided seeds.
Percolation brewing: A method where fresh water continuously passes through a bed of coffee and exits as brewed beverage, as in pour-over and most drip brewers.
Permeability: How easily fluid can pass through a porous coffee bed or espresso puck. Grind size, fines, puck preparation, swelling, and dose all influence permeability.
pH: A logarithmic measure of hydrogen-ion activity indicating how acidic or basic a solution is. For brew water, alkalinity is often more predictive of coffee-acid buffering than pH alone.
Phin: A Vietnamese metal drip brewer that uses gravity to pass water slowly through coffee, commonly served with condensed milk.
Piccolo latte: A small milk drink using espresso or ristretto with textured milk, typically served in a small glass.
PID controller: A proportional-integral-derivative control system used to regulate temperature more precisely than a simple on/off thermostat or pressurestat in many espresso machines.
Piston seal: A seal around a lever-machine piston that prevents water bypass while allowing the piston to move through the group cylinder.
Pitcher rinser: A sink-mounted or counter-mounted spray device activated by pressing a pitcher or glass onto a star or plate, used to quickly rinse milk pitchers.
Popcorning: Beans bouncing upward in a nearly empty grinder throat or hopper because of rotating burr airflow and impact, which can make final beans feed less consistently.
Portafilter: The removable handled filter holder that locks into an espresso-machine grouphead and holds the filter basket.
Portafilter fork: A grinder support that holds a portafilter beneath the grounds chute for hands-free or guided dosing.
Portion-control grinder: A commercial grinder that dispenses a preset dose or quantity for batch brewing or other preparation.
Pour rate: The mass or volume of water added per unit of time during manual brewing.
Pour-over: A manual percolation brewing method where hot water is poured over coffee in a filter and passes through the bed by gravity.
Pouring height: The vertical distance between kettle spout and slurry. It affects stream energy, agitation, and how deeply the stream penetrates the slurry.
Pre-breaker teeth: The initial burr teeth or features that fracture whole beans into smaller pieces before finer cutting zones finish the grind.
Pre-brew: A programmable wetting pattern in which water is applied and then stopped for a pause before full brewing. Some manufacturers distinguish this stop-start behavior from continuous low-pressure pre-infusion.
Pre-infusion: The initial wetting of an espresso puck at reduced pressure or flow before full extraction pressure, intended to improve saturation and manage puck resistance.
Precision basket: An espresso basket manufactured with tightly controlled hole size, pattern, geometry, and tolerances to promote repeatable flow.
Pressure gauge: An instrument that displays fluid or steam pressure in a machine.
Pressure manipulation: Any deliberate change to brew pressure during extraction, including ramps, declining profiles, lever profiles, or manual control.
Pressure profiling: Deliberately changing brew pressure over the course of an espresso shot rather than holding one fixed pressure.
Pressure ramp: A programmed or manual increase in pressure from a lower starting level toward a target pressure during extraction.
Pressure regulator: A plumbing device that reduces and stabilizes incoming water pressure to a level suitable for the equipment.
Pressurestat: A pressure-operated switch that cycles a heating element to maintain steam-boiler pressure within a range.
Preventive maintenance: Scheduled inspection, cleaning, lubrication, adjustment, and part replacement intended to prevent failures and maintain consistent equipment performance.
Prosumer espresso machine: A non-regulated market term for robust home machines that borrow features, construction, or thermal architecture from commercial equipment.
Puck integrity: The structural continuity of the prepared coffee bed. Cracks, edge gaps, and disturbed surfaces can create low-resistance paths and channeling.
Puck preparation: The sequence used to dose, distribute, level, and tamp espresso grounds before brewing.
Puck resistance: The opposition to water flow created by the compacted coffee bed. Grind size, dose, basket, puck prep, swelling, and extraction all affect it.
Puck screen: A thin perforated or mesh screen placed on top of an espresso puck to spread water, reduce shower-screen contamination, and sometimes alter headspace or flow.
Puck screen contact: A condition where the puck or puck screen touches the shower screen before or during brewing. Some contact can be normal after swelling, but excessive initial contact can disturb the puck.
Puck sticking to shower screen: A puck that adheres to the group after removing the portafilter, often caused by puck swelling, tight headspace, surface suction, or coffee dose.
Puck swelling: Expansion of the coffee bed as grounds absorb water during pre-infusion and extraction.
Pulse pouring: Dividing pour-over water into multiple distinct pours separated by pauses rather than pouring continuously.
Pump pressure: Pressure measured in the machine's pump or brew circuit. It is not always identical to pressure at the coffee puck.
Purge: Grinding and discarding a small amount of coffee to clear stale grounds, transition between beans, or stabilize a new grind setting.
Purge steam wand: Briefly opening the steam valve before or after steaming to clear condensation or residual milk from the steam tip.

Q

Q Grader: A coffee professional trained and calibrated through a formal quality-evaluation program to assess coffee using established sensory protocols.

R

Radial alignment: Alignment relating to whether burrs and carriers are centered concentrically around the grinder's rotational axis.
Radiation: Heat transferred by electromagnetic radiation from hot surfaces or flame without requiring direct contact.
Raised drying bed: An elevated mesh or screen bed that allows air to circulate around drying coffee and facilitates sorting and turning.
Raised group: A commercial espresso-machine group configured with extra cup clearance for tall takeaway cups, often with a fold-down or removable support for small espresso cups.
Rate of rise: The rate at which a measured roast temperature is changing, typically expressed as degrees per unit of time.
RDT: Ross Droplet Technique: adding a very small amount of water to whole beans before grinding to reduce static and grounds spray.
Recovery time: The time required for equipment to restore target temperature, pressure, or energy after brewing, steaming, or hot-water demand.
Red Speed burr: A trade name used for a hard red-colored burr coating found on some premium burr sets; exact composition and performance depend on manufacturer.
Refractometer: An optical instrument that measures refractive index and can be calibrated to estimate coffee beverage TDS.
Regrinding: Ground particles re-entering or remaining in the burr path and being ground again, potentially affecting fines, heat, and particle distribution.
Remineralization: Adding selected minerals back to low-mineral or reverse-osmosis water to create a target brewing-water composition.
Retention: Coffee that remains inside a grinder after grinding rather than exiting with the intended dose.
Reverse osmosis: A membrane process that removes a large proportion of dissolved ions and contaminants by forcing water through a semi-permeable membrane.
Ristretto: A shorter espresso with a lower beverage yield relative to dose than a normale, often around or below roughly 1:1.5 depending on convention.
Roast curve: A graph of roast variables over time, commonly including bean temperature, environmental temperature, rate of rise, gas or power, airflow, and drum speed.
Roast development: The degree to which roasting reactions have progressed enough to create desirable flavor, structure, and solubility. Development is not synonymous with simply roasting darker.
Roasted coffee: Coffee beans after roasting has developed aroma, flavor, color, and solubility.
Robusta: A common name for Coffea canephora, a coffee species often associated with higher caffeine, strong body, bitterness, and greater heat and disease tolerance than arabica.
Rolling milk: Creating a strong whirlpool or circulation after initial aeration to fold bubbles into the milk and improve texture.
Rosetta: A classic latte-art pattern resembling a fern or leaf, made with a side-to-side wiggle and pull-through.
Rotary vane pump: A motor-driven positive-displacement pump common in commercial and prosumer machines, known for quieter operation, strong flow, and easy pressure adjustment.
RTD: A resistance temperature detector that estimates temperature from predictable changes in electrical resistance, often valued for stability and accuracy.

S

Salami shot: A diagnostic tasting method in which successive portions of one espresso extraction are collected in separate cups to taste how flavor changes over time.
Sample roaster: A small coffee roaster used to evaluate green coffee samples or develop roast approaches before larger production roasting.
Satellite brewer: A commercial batch brewer that brews into removable insulated servers or satellites that can be moved to serving stations.
Saturated group: A grouphead thermally integrated with or directly exposed to the brew-boiler water environment to improve temperature stability.
Saturation: The state in which grounds are thoroughly wetted with brewing water. Uneven initial saturation can contribute to uneven extraction.
Scale inhibitor: A treatment media or chemical that reduces mineral scale formation without necessarily removing all hardness.
Scaling potential: The tendency of water to precipitate mineral deposits under equipment conditions, influenced by hardness, alkalinity, pH, temperature, and concentration.
Scorching: Dark burned-looking marks on bean surfaces caused by excessive conductive heat or poor heat management.
Second crack: A later series of lighter, more rapid crackling sounds associated with deeper roasting and breakdown of bean structure.
Sediment filter: A filter that removes suspended particles such as sand, rust, or debris before finer treatment stages.
Selective picking: Harvesting only cherries at the desired ripeness while leaving under-ripe fruit for later passes, typically done by hand.
Self-leveling tamper: A tamper with a guide or flange that references the basket rim to help keep the tamping face level.
Semi-automatic espresso machine: A machine where the barista starts and stops brewing manually, while an electric pump supplies brew pressure.
Semi-saturated group: A group design thermally connected to the brew boiler but not fully immersed or saturated in the same way as a classic saturated group.
Semi-washed coffee: A broad term used for processing styles that remove some fruit before final drying but do not follow a classic fully washed process. Usage varies by origin.
Shade-grown coffee: Coffee cultivated under partial tree canopy rather than full sun. Shade can influence ecology, maturation, farm management, and microclimate.
Shimming: Placing very thin material under selected points of a burr or carrier to correct alignment.
Shot counter: A machine function that records brew cycles or doses for maintenance, usage analysis, or café management.
Shot profile: The planned sequence of pressure, flow, temperature, and timing stages used during an espresso extraction.
Shot time: The elapsed time used to describe an espresso extraction. Timing conventions differ, so recipes should state whether time begins at pump activation, first drip, or another point.
Shot timer: A timer integrated into a machine, scale, or external device that tracks espresso extraction time.
Shower screen: The perforated screen at the bottom of the group that spreads brew water over the espresso puck and helps keep grounds out of the group.
Shower-screen replacement: Replacing a damaged, clogged, worn, or upgraded espresso group shower screen.
Shutoff valve: A manual valve installed in a water supply line so equipment can be isolated for service or emergencies.
Side tapping: Tapping the portafilter side to settle or redistribute grounds. Excessive tapping after tamping can fracture the puck and is generally avoided.
Silica: Dissolved silicon compounds in water that can form stubborn deposits and are not removed effectively by conventional ion-exchange softeners.
Silverskin: A thin papery layer attached to the coffee seed. Much of it separates during roasting and becomes part of the chaff.
Single boiler: An espresso machine with one main boiler used for brewing and, depending on design, steaming. Some require switching temperatures between brew and steam.
Single boiler dual use: A single-boiler machine that alternates the same boiler between brew temperature and higher steam temperature rather than brewing and steaming simultaneously.
Single espresso: An espresso prepared with a smaller single basket or recipe, traditionally yielding one serving. Modern cafés often use double baskets even for single-drink orders.
Single phase: An AC electrical supply using one alternating voltage phase, common in homes and many cafés.
Single-dose grinder: A grinder designed to grind one pre-weighed dose at a time rather than storing a large quantity of beans in a hopper.
Single-origin coffee: Coffee identified with one geographic source, such as a country, region, farm, cooperative, or individual lot, rather than a blend of multiple origins.
Sink shot: Barista slang for an espresso shot judged poor enough to discard rather than serve or drink.
Siphon brewer: A vacuum brewer using vapor pressure and cooling vacuum to move water between chambers and brew coffee through a filter.
SL28: An arabica selection developed in Kenya and known for excellent cup quality, often showing intense fruit, sweetness, and vibrant acidity.
SL34: A Kenyan arabica selection widely planted for agronomic performance and cup quality, frequently associated with classic Kenyan flavor profiles.
Slow feeding: Intentionally feeding beans into the burrs gradually rather than all at once, which can change particle distribution, fines production, and throughput on some grinders.
Slow shot: An espresso extraction that reaches the target yield too slowly for the intended recipe, commonly corrected with a coarser grind or lower dose after checking for clogs and prep issues.
Slurping: Drawing coffee quickly from a cupping spoon across the palate to distribute it widely and improve sensory evaluation.
Smallholder: A producer farming a relatively small area, often delivering cherries or parchment to a cooperative, washing station, or local mill.
Sodium: A mineral ion in water that does not contribute to hardness but can influence taste and may be introduced by sodium-cycle water softeners.
Soft infusion: A low-pressure or reduced-flow opening phase intended to wet the puck gently before full extraction.
Solid-state relay: An electronic switching device often used by PID-controlled machines to rapidly cycle a heating element without a mechanical relay.
Solubles: Coffee compounds that dissolve into brewing water, contributing to beverage strength, aroma, taste, and color.
Soupy puck: An espresso puck with standing water or loose slurry after brewing, often related to generous headspace or machine venting and not necessarily a problem if the espresso tastes good.
Sour espresso: Espresso dominated by sharp sourness. It may result from low extraction, an unsuitable recipe, low temperature, very light roast solubility, or simply the coffee's intended acidity.
Specialty coffee: Coffee recognized for distinctive attributes and added value created through quality, sensory character, provenance, production, processing, roasting, preparation, or other meaningful characteristics. Historically, “80+ points” was widely used as a shorthand threshold, but current specialty-coffee evaluation is broader than a single cupping score.
Read the full guide: What Is Specialty Coffee?
Spouted portafilter: A portafilter that directs espresso from the basket through one or more spouts into cups.
Sprayhead: The perforated or slotted component in an automatic drip brewer that distributes hot water over the coffee bed.
Spraying bottomless portafilter: Visible jets or sprays from a bottomless basket, usually indicating localized channeling, puck damage, or uneven distribution.
Spring lever: A lever group in which the barista compresses a spring and the spring then drives the piston through a declining-pressure extraction.
Sprover: A low-pressure, high-ratio espresso-machine brew that behaves more like a small percolation filter coffee than conventional espresso.
Stainless-steel burr: A burr manufactured from a stainless-steel alloy, chosen for corrosion resistance and specific wear or machining properties.
Stalled brew: A filter brew whose drawdown becomes unusually slow or nearly stops, often because fines clog filter pores or migrate to restrictive areas.
Static: Electrical charge generated during grinding that can make grounds cling to the grinder, cup, chute, or surrounding surfaces.
Static pressure: Pressure measured when fluid is not flowing. It can differ substantially from dynamic pressure during brewing.
Steam boiler: A boiler operated above atmospheric boiling temperature to provide steam and often hot water for service.
Steam pressure: The pressure available from the steam boiler or steam system. Higher pressure can increase steam velocity and milk-texturing power.
Steam pressure loss: Insufficient steam pressure during use, which can result from low boiler set point, inadequate recovery, heating faults, scale, heavy simultaneous demand, or steam-system restrictions.
Steam recovery: How quickly an espresso machine rebuilds steam-boiler pressure and temperature after steaming or dispensing hot water.
Steam tip: The removable nozzle at the end of a steam wand containing one or more holes that shape steam jets.
Steam wand: The metal tube used to deliver steam from an espresso machine into milk or other liquids.
Steam-wand cleaning: Wiping the wand immediately after steaming and purging steam to prevent milk from drying inside or on the tip.
Stepless adjustment: A grind-adjustment system without fixed click positions, allowing continuous changes within its mechanical range.
Stepped adjustment: A grind-adjustment system with discrete click or detent positions.
Stir: Using a spoon, paddle, or stick to mechanically agitate the coffee slurry.
Stockfleth's move: A traditional hand-distribution technique that uses a finger and rotating movement to level espresso grounds across the basket before tamping.
Strength: The concentration of dissolved coffee solids in the beverage. Strength is commonly measured as total dissolved solids and is different from extraction yield.
Stretching milk: Barista term for adding air to milk with the steam tip near the surface so the milk volume increases.
Strip picking: Harvesting most or all cherries from a branch in one pass, regardless of individual cherry ripeness.
Sulfate: A common water ion that affects ionic balance and taste. High concentrations can contribute to scaling or flavor changes depending on overall chemistry.
Superautomatic espresso machine: A bean-to-cup machine that automates grinding, dosing, brewing, and usually beverage cleanup; many also automate milk drinks.
Sweetness: The perception of sugars and sweet-associated aromas in coffee, often expressed as caramel, fruit, honey, chocolate, or other sweet impressions.
Swirl: Rotating the brewer or slurry in a circular motion to mix grounds, level the bed, or manage bloom and drawdown.

T

Tamper: The handheld or automated tool used to compress coffee in an espresso basket.
Tamping: Compressing and leveling ground coffee in an espresso basket to create a stable, even puck.
Tamping mat: A protective mat placed under a portafilter while tamping to protect the counter and improve stability.
Tamping station: A support that holds a portafilter securely and level during tamping.
Temperature instability: Excessive variation in brew or steam temperature across time or repeated cycles, potentially related to control, scale, sensors, thermal design, warm-up, or workload.
Temperature offset: A programmed correction between the temperature measured at a sensor and the estimated or desired temperature at another point, such as the coffee puck.
Temperature probe: A sensor used by an espresso machine or roaster to measure temperature for control, display, or safety.
Temperature stability: The ability of brewing equipment to maintain a consistent temperature during a brew and from one brew to the next.
Temperature surfing: A technique used especially on thermostat-controlled single-boiler machines to time brewing within the heater's temperature cycle for better repeatability.
Thermal carafe: An insulated serving vessel designed to retain coffee temperature without a hot plate.
Thermal mass: The heat-storing capacity of a component or system. High thermal mass can resist temperature changes but can also require longer warm-up.
Thermal shock process: An experimental processing approach that intentionally applies rapid temperature changes to coffee or fermentation material. Exact protocols differ by producer.
Thermoblock: A compact flow-through heater where water passes through channels in a heated metal block, allowing rapid heating without a conventional large boiler.
Thermocoil: A flow-through heating system using a heated metal tube or coil, conceptually similar to a thermoblock but differing in construction.
Thermosiphon: A natural circulation loop in which hot water rises and cooler water falls, commonly used to keep E61 and other groups hot from a boiler or heat exchanger.
Thermosiphon stall: Reduced or stopped natural circulation in a thermosiphon loop, potentially causing an E61 or similar group to run cooler than intended.
Thermostat: A temperature-sensitive switch or control used to maintain or limit temperature in boilers, thermoblocks, groups, or safety circuits.
Thin espresso: Espresso with low perceived body or intensity, potentially caused by low strength, high yield, channeling, coffee choice, or clarity-focused grind characteristics.
Third-wave coffee: A movement that treats coffee as a craft product with emphasis on origin, processing, fresh roasting, precise brewing, and transparent sourcing.
Three phase: An AC power system using three phase conductors offset in time, common in larger commercial installations and some high-power equipment.
Three-group espresso machine: A commercial espresso machine with three brew groups for high-volume bars that need greater simultaneous shot capacity.
Three-way solenoid valve: An electrically controlled valve that directs brew water during extraction and then vents pressure from the group to the drain when the shot ends.
Throughput: The amount of product or number of beverages equipment can process over a period of time under practical operating conditions.
Tiger striping: Alternating darker and lighter streaks sometimes visible in espresso crema. It can look attractive but is not a reliable standalone measure of shot quality.
Timed dosing: Controlling grinder dose by running the motor for a programmed duration. Dose mass can still vary with beans, grind setting, hopper level, and conditions.
Tipping: A roast defect where the tips of beans show localized scorching, often associated with excessive heat intensity or particular bean characteristics.
Titanium-coated burr: A burr with a titanium-based surface coating, often titanium nitride or a related coating, applied for wear resistance and surface characteristics.
Torque: Rotational force produced by a grinder motor at the burrs. Adequate torque helps maintain speed under grinding load.
Total dissolved solids: An estimate of the concentration of dissolved material in a beverage, usually reported as a percentage for brewed coffee or espresso.
Total retention: The total mass of coffee physically held inside a grinder at a given time, including material that may remain for many subsequent doses.
Traceability: The ability to follow a coffee back through the supply chain to information such as exporter, cooperative, washing station, farm, producer, plot, process, and harvest.
Triangulation: A sensory test using three samples, usually two identical and one different, where the taster tries to identify the odd sample.
Tulip: A latte-art pattern built by stacking multiple pushed layers or hearts and finishing with a cut-through.
Turbo shot: A modern espresso style using a relatively coarse grind, lower resistance, fast flow, and often lower pressure to produce high extraction in a short shot time.
Turbulence: Irregular fluid motion in the coffee slurry or espresso puck that can increase mixing and mass transfer.
Turkish coffee: A brewing method using extremely fine coffee heated in a cezve or similar pot and served unfiltered so fine grounds settle in the cup.
Turning point: The early roast moment when the displayed bean-temperature curve stops falling after charge and begins rising. It is largely a probe-and-heat-balance phenomenon rather than the beans literally cooling to that exact point.
Two-group espresso machine: A commercial espresso machine with two brew groups, the most common configuration for many cafés because two baristas or multiple shots can be handled efficiently.
Typica: A foundational arabica variety from which many modern coffee varieties descend, known for good cup quality but generally modest yield and disease susceptibility.

U

UL certification: A safety listing or certification associated with UL Solutions and applicable electrical or equipment standards.
Ultrafines: The extreme small-particle tail of a grind distribution, finer than what is generally meant by ordinary fines.
Unbleached filter: A brown paper filter that has not been whitened. Rinsing can reduce papery flavor in either bleached or unbleached filters.
Under-extraction: A condition where too little desirable soluble material has been removed from the coffee for the intended recipe, often associated with sourness, thinness, salinity, or incomplete sweetness.
Underdeveloped roast: A roast in which internal flavor development is insufficient, often producing vegetal, grainy, peanut-like, sharply acidic, or difficult-to-extract characteristics.
Unimodal distribution: A distribution dominated by one main particle-size peak, often used loosely in coffee to describe clarity-focused burr sets with fewer fines.
Upgrade path: A planned sequence of equipment improvements, often prioritizing the grinder, water quality, and workflow before less impactful accessories.

V

V60: Hario's cone-shaped pour-over brewer with a large bottom opening and spiral ribs, commonly used with thin paper filters.
Vacuum breaker: A steam-boiler valve that vents air while the boiler heats and closes once steam pressure develops, helping prevent false pressure and vacuum formation.
Variable RPM: A grinder feature that lets the user change burr rotational speed. RPM can affect feed behavior, throughput, particle distribution, and workflow depending on the grinder.
Variable-temperature kettle: An electric kettle that lets the user select and maintain a target water temperature.
Vibration pump: A compact electromagnetic reciprocating pump common in home espresso machines. It produces pressure through rapid piston movement and typically has a distinctive buzzing sound.
Voltage: Electrical potential difference, measured in volts. Coffee equipment must be matched to the supply voltage for which it is designed.
Volumetric espresso: Espresso dosing controlled by measured water flow or volume rather than beverage weight.
Volumetric espresso machine: A machine that can stop a brew automatically after measuring a programmed water volume or flowmeter count.
Volumetric programming: The process of teaching an automatic espresso machine the target flowmeter count or volume for each brew button.

W

Washed process: A process in which most fruit is removed before drying, typically through pulping, fermentation or mechanical demucilaging, washing, and parchment drying.
Washing station: A facility where freshly harvested coffee cherries are received and processed, especially in regions where many small producers deliver cherries to a centralized site.
Water activity: A measure of how available water is for chemical reactions and microbial activity. It can provide storage information beyond moisture percentage alone.
Water backflush: Backflushing with plain water to remove loose coffee residue from the group and exhaust path.
Water debit: The free-flow rate of water from a group without a coffee puck, often measured to diagnose restrictors, pump performance, or group flow.
Water filter: A cartridge or system designed to remove or reduce specific contaminants, tastes, odors, hardness, sediment, or scale-forming minerals.
Water hardness: The concentration of multivalent minerals in water, primarily calcium and magnesium. Hardness affects flavor, extraction, and scale formation.
Water inlet: The connection where a plumbed coffee machine receives its water supply.
Water reservoir: A removable or built-in tank that supplies water to a non-plumbed espresso machine.
Water softener: A system that reduces hardness ions, commonly through sodium-cycle ion exchange, to limit limescale formation.
Water TDS: A broad estimate of dissolved ionic material in water. TDS alone cannot reveal which minerals are present or predict brewing suitability.
Water test strip: A disposable strip that estimates one or more water parameters such as hardness, alkalinity, chlorine, or pH through color changes.
Wattage: Electrical power consumption or heating capacity, measured in watts. Watts equal volts multiplied by amps in a simple resistive load.
WDT: Weiss Distribution Technique: stirring or raking espresso grounds with thin needles to break clumps and improve distribution before tamping.
WDT tool: A puck-preparation tool with thin needles used for Weiss Distribution Technique.
Weak coffee: Coffee with lower concentration than desired. Strength can usually be increased by using more coffee, less beverage water, or adjusting extraction and bypass appropriately.
Wet puck: An espresso puck that remains visibly wet after brewing. Puck wetness alone is not a reliable indicator of shot quality and can depend on headspace, machine design, and basket.
Wet steam: Steam containing more liquid water droplets, which can reduce texturing efficiency and add more water to milk.
Wet-hulled process: A processing method common in Indonesia in which parchment is hulled while the coffee still has relatively high moisture, then the exposed green coffee is dried further.
Worm-drive adjustment: A fine-adjustment mechanism where a worm gear turns the grinder's collar or burr carrier in small increments.

X

No glossary terms currently begin with X.

Y

Yeast inoculation: The deliberate addition of selected yeast cultures to coffee fermentation to influence consistency, kinetics, or flavor development.
Yellowing: The stage when green coffee visibly turns yellow or tan and grassy aromas transition toward bread, cereal, or hay-like aromas.
Yield: The mass or volume of brewed beverage produced. In espresso, yield usually means the liquid espresso mass in the cup.

Z

Zero point: A grinder reference point near where the burrs first touch or reach the minimum intended spacing. Printed zero markings do not always equal physical burr contact.
Zero-retention grinder: A marketing term for a grinder designed to minimize retained grounds. In practice, no grinder is literally guaranteed to retain zero coffee under all conditions.