The Coffee Glossary
From botanicals to boiler parts—your complete guide to the world of espresso.
Arabica
The premium species of coffee, known for its acidity and sweetness. Grows best at high altitudes.
Automatic Machine
A machine that uses a flow meter to stop the coffee delivery at a pre-set volume.
Acidity
A positive flavor trait in coffee, often described as brightness or "tang" (e.g., citrus or berry notes).
Aeropress
A manual brewer using a piston to force coffee through a thin paper filter.
Americano
An espresso shot topped up with hot water to mimic the strength of drip coffee.
Backflushing
The process of cleaning a machine's internals by forcing water/detergent back through the grouphead via a blind filter.
Bean-to-Cup
A machine that integrates a grinder and brewing unit to go from whole beans to coffee automatically.
Blend
A mix of different coffee beans designed to create a consistent, balanced flavor profile.
Blind Filter
A solid basket with no holes, used for cleaning the grouphead.
Burrs
The rotating plates in a grinder that crush beans. Can be Flat or Conical.
Boiler
The pressurized tank where water is heated for brewing and steam.
Body
The "weight" or mouthfeel of the coffee on the tongue (e.g., watery vs. syrupy).
Bar
The unit of pressure. Standard espresso is brewed at 9 Bars of pressure.
Crema
The golden, aromatic froth on top of an espresso shot made of CO2 and emulsified oils.
Cupping
The professional process of tasting coffee to evaluate its quality.
Channelling
When water finds a crack in the coffee puck, leading to uneven and poor-tasting extraction.
Cappuccino
A 6oz drink made of equal parts espresso, steamed milk, and milk foam.
Cortado
Espresso "cut" with a small amount of warm milk to reduce acidity.
Chemex
A pour-over glass brewer known for its thick filters that produce a very clean cup.
Degassing
The release of CO2 from roasted beans. Essential to wait a few days after roasting for the best flavor.
Dose
The weight of dry coffee grounds used (e.g., 18 grams for a double espresso).
Descaling
Removing mineral/limescale buildup from the boiler and heat exchanger.
Doser
The chamber on a grinder that dispenses coffee via a lever mechanism.
Direct Trade
When roasters buy beans directly from the farmers, often paying higher than Fair Trade prices.
Espresso
A 25-35ml concentrated coffee brewed under 9 bars of pressure.
Extraction
The process where water dissolves the coffee's flavor. Under-extraction is sour; over-extraction is bitter.
E61 Group
A classic, heavy-duty grouphead design featuring a pre-infusion chamber and thermal stability.
Ethical Sourcing
Ensuring coffee is grown and traded in a way that supports workers and the environment.
Filter Coffee
Coffee brewed by gravity through a paper or metal filter (e.g., drip or pour-over).
Flat White
An espresso with a thin layer of velvety microfoam milk.
French Press
An immersion brewer where coffee steeps in water before being filtered by a metal mesh plunger.
Frothed Milk
Milk that has been aerated to create large, airy bubbles.
Grinder
The equipment used to break down beans. Burr grinders are essential for espresso.
Grouphead
The interface where the portafilter meets the machine's water delivery system.
Group Gasket
The rubber/silicone ring that seals the portafilter to the grouphead.
Green Beans
Raw, unroasted coffee beans.
Hopper
The bin on top of the grinder that holds the beans.
Heat Exchanger (HX)
A boiler system that allows brewing and steaming at the same time by running brew water through a pipe inside the steam boiler.
Hull
The outer skin of the coffee cherry removed during processing.
Immersion
A brewing method where coffee grounds are fully submerged in water (e.g., French Press).
Italian Roast
A very dark, oily roast of coffee with intense, smoky flavors.
Java
A slang term for coffee, originally referring to coffee grown on the island of Java.
Jug (Milk)
A stainless steel pitcher used for steaming milk.
Kettle (Gooseneck)
A kettle with a thin, curved spout used for precision pouring in drip coffee.
Knock Box
A bin with a bar across it used to "knock" the spent coffee puck out of the portafilter.
Latte
Espresso with a large amount of steamed milk and a small layer of foam.
Latte Art
Patterns created by pouring microfoam into espresso.
Lever Machine
An espresso machine where the user pulls a lever to create the pressure needed to brew.
Microfoam
Finely textured steamed milk with tiny, uniform bubbles, used for professional-quality drinks.
Moka Pot
A stovetop brewer that uses steam pressure to push water through coffee grounds.
Macchiato
Espresso "marked" with a tiny dollop of milk foam.
Naked Portafilter
A portafilter with no bottom, allowing you to see the espresso flow directly from the basket.
Notes
Individual flavor characteristics (e.g., "chocolate notes" or "floral notes").
Over-extraction
Occurs when coffee is brewed too long or too fine, resulting in a bitter, astringent taste.
OPV (Over Pressure Valve)
A valve that regulates the maximum pressure of the machine, usually set to 9 bar.
Portafilter
The handle and basket used to hold the coffee during extraction.
Puck
The spent, compressed coffee grounds after brewing.
Pre-infusion
Gently wetting the coffee puck at low pressure before full brewing begins.
PID
A digital controller that maintains a highly stable water temperature in the boiler.
Piston
The part of a lever machine or Aeropress that pushes water through the coffee.
Robusta
A coffee species with higher caffeine and a more bitter, earthy flavor than Arabica. Often used for crema.
Ristretto
A "restricted" shot. Same amount of coffee but less water, making it sweeter and more intense.
Roasting
The process of heating green beans to transform their chemical and physical properties into drinkable coffee.
Steam Wand
The metal pipe used to heat and texture milk with steam.
Steamed Milk
Milk that has been heated and "stretched" with a steam wand to create texture.
Solenoid Valve
An electric valve that controls the flow of water and releases pressure (the 3-way valve).
Single Origin
Coffee sourced from one single farm or region.
Shower Screen
A mesh screen in the grouphead that disperses water evenly over the coffee.
Scale
Essential tool for weighing dry coffee and liquid espresso for consistency.
Tamper
The tool used to compress coffee grounds into a flat, level puck.
Thermistor
A sensor that tells the machine's computer what the water temperature is.
Terroir
The environmental factors (soil, climate) that give a coffee its unique flavor.
Tamping
The act of pressing the grounds down to ensure even water resistance.
Under-extraction
Occurs when water passes through the coffee too quickly, leaving it sour and thin.
UPP (Under Pressure)
A term used when a machine is not reaching the 9-bar standard required for espresso.
Volumetric
A machine feature that measures the volume of water dispensed to ensure shot consistency.
V60
A popular cone-shaped pour-over dripper made by Hario.
Vibration Pump
A small, affordable pump found in home espresso machines that uses a piston and magnet.
Water Softener
A filter used to remove minerals from water to prevent limescale damage to coffee machines.
Whole Bean
Coffee that has been roasted but not yet ground.
WDT
Weiss Distribution Technique. Using thin needles to break up clumps in the coffee grounds before tamping.
Yield
The final weight of the liquid espresso in the cup (e.g., 18g dry dose = 36g yield).