A reference for every espresso term you’ll encounter — whether you’re reading a recipe, setting up your machine for the first time, or trying to understand what a barista means when they talk about “extraction yield” or “channeling.”

Organized alphabetically. Each entry links to the full guide where one exists.

A

Affogato An Italian dessert made by pouring a hot espresso shot over vanilla gelato or ice cream. The name means “drowned” in Italian. One of the simplest espresso preparations — two ingredients, served immediately. → Full guide

AeroPress A manual brewing device that uses air pressure to push water through coffee grounds. Can produce a strong, espresso-like concentrate, though not true espresso (lacks the 9 bars of pressure). Popular for travel and experimentation.

Americano (Caffè Americano) Espresso diluted with hot water, typically in a 1:3 ratio (1 part espresso to 3 parts water). Origin story: American soldiers in WWII Italy diluted local espresso to approximate drip coffee. The result tastes different from drip coffee because it starts from espresso crema. → Full guide

Aroma The scent of brewed espresso. A complex mixture of volatile compounds including aldehydes, furans, and acids. Aroma degrades quickly after brewing — drink espresso fresh.

B

Backflush A cleaning method for espresso machines with a three-way solenoid valve. A blind filter basket (no holes) forces water and cleaning solution back through the group head. Required for machines like the Gaggia Classic Pro, Breville Bambino. Not all machines support it.

Basket (Filter Basket) The perforated metal cup inside the portafilter that holds the ground coffee. Baskets come in single (7-9g), double (14-18g), and triple (21g+) sizes. Basket diameter and depth affect extraction. Aftermarket precision baskets (VST, IMS) have more consistent perforation patterns.

Blonde Espresso Starbucks’ name for a lighter roast espresso blend. “Blonde” means lighter roast, not a different species or processing method. Lighter roasts have more caffeine by mass than dark roasts.

Bloom In filter/pour-over coffee, the initial pour of hot water that causes CO₂ to release from fresh grounds (making the coffee “bloom” or puff up). Less relevant for espresso but important in other methods.

Body The perceived weight or thickness of espresso in the mouth. A full-body espresso feels substantial; a thin-body espresso feels watery. Body is affected by extraction, roast level, and the dissolved solids in the cup (measured as TDS).

C

Caffè Crema A long espresso drink popular in Switzerland, Germany, and Austria. Similar to a lungo but typically pulled at lower pressure and using more coarsely ground coffee. Not to be confused with crema (the foam layer on espresso).

Caffeine The primary stimulant in espresso. A double shot contains approximately 60-120mg, depending on the bean variety, roast level, and extraction. Robusta beans have about twice the caffeine of Arabica. → Full guide: Espresso Caffeine

Cappuccino A traditional Italian espresso drink made with equal parts espresso, steamed milk, and milk foam — traditionally served in 150-180ml. The foam layer distinguishes it from a latte. “Wet cappuccino” has more steamed milk; “dry cappuccino” has more foam. → Full guide

Channeling A defect in espresso extraction where water finds a path of least resistance through the coffee puck rather than percolating evenly. Channeling causes uneven extraction (some coffee over-extracted, some under-extracted) and produces bitter, thin, or sour espresso. Caused by uneven distribution, poor tamping, or a damaged puck.

Cortado A Spanish espresso drink: equal parts espresso and steamed milk (about 1:1 ratio). The milk cuts (cortado = “cut” in Spanish) the acidity of the espresso without dominating it. Smaller than a latte, larger than a macchiato. → Full guide

Crema The golden-brown foam that forms on top of a freshly pulled espresso shot. Created when CO₂ gas, released from freshly roasted beans during extraction, is emulsified with water and coffee oils. A sign of fresh beans and proper extraction. Crema dissipates within minutes. → Full guide

D

Dial In The process of adjusting grind size, dose, and extraction time to hit target parameters for a specific coffee. A new bag of beans often requires dialing in because roast level, freshness, and origin affect extraction rate.

Doppio Italian for “double.” A doppio espresso is a double shot — two shots pulled together into one cup, typically 60ml. The standard espresso order at most Italian bars. “Can I get a doppio?” is asking for a standard double espresso. → Full guide

Dose The weight of dry coffee grounds used in a portafilter basket, measured in grams. A standard double dose is 14-18g depending on the basket. Part of the espresso ratio (dose in : yield out).

Distribution The process of evenly spreading ground coffee across the basket before tamping. Uneven distribution leads to channeling. Techniques: Weiss Distribution Technique (WDT), tapping the portafilter, or using a distribution tool.

E

E61 Group Head A group head design invented in 1961 by Faema, widely used in prosumer and commercial machines. Features a thermosiphon system for temperature stability and pre-infusion capability. Found on many popular home espresso machines.

Espresso Coffee brewed by forcing hot water (90-96°C) at high pressure (8-10 bars) through finely ground, tightly packed coffee. Produces a small, concentrated shot (typically 25-35ml) with a layer of crema. Espresso is the base for most café drinks (latte, cappuccino, americano, etc.). → Getting started guide

Espresso Beans There is no botanical species called “espresso beans.” Any coffee bean can be used for espresso — the term refers to the intended use or the roast style (typically medium-dark to dark roast). → Full guide

Espresso Machine A machine that brews espresso. Categories:

  • Semi-automatic: You grind, dose, tamp; machine controls water pressure
  • Automatic: Automates the water volume
  • Super-automatic: Grinds and brews automatically with minimal user input
  • Manual/lever: User controls pressure manually

→ Best Espresso Machines for Beginners

Espresso Ratio The ratio of dry coffee dose to liquid yield, expressed as 1:X. A standard espresso ratio is 1:2 (e.g., 18g in, 36g out). Ristretto pulls shorter (1:1 to 1:1.5); lungo pulls longer (1:3+). → Full guide

Extraction The process of dissolving flavor compounds from coffee grounds into water. Under-extracted coffee tastes sour, weak, and thin. Over-extracted coffee tastes bitter, harsh, and astringent. Well-extracted espresso hits a balance of sweetness, acidity, and bitterness.

Extraction Yield The percentage of coffee grounds dissolved into the final brew. Target for espresso: 18-22%. Measured using a refractometer (TDS meter). Most home baristas never measure this directly and instead dial in by taste and ratio.

F

Fines Very small particles produced by grinding. All grinders produce some fines. Excessive fines cause over-extraction and bitterness. Fines migration (fines moving into the drip tray) indicates channeling.

Flat White An espresso drink originating in Australia/New Zealand. Similar to a latte but smaller (160-180ml) with a higher espresso-to-milk ratio and thinner microfoam (no foam layer). The espresso flavor is more pronounced than in a latte. → Full guide

Flow Rate The speed at which water passes through the coffee puck during extraction, measured in ml/second. Related to grind size — finer grind slows flow rate. Target for espresso: roughly 1-2ml/second.

Foam Air bubbles in steamed milk. Distinct from microfoam — regular foam has large, visible bubbles and a dry, airy texture. Microfoam has very small bubbles and a smooth, velvety texture. Cappuccinos have a layer of foam; lattes use microfoam throughout.

G

Grind Size How coarsely or finely coffee is ground. Espresso requires a fine grind — finer than any other brewing method. Grind size is the primary variable for adjusting extraction time. → Full guide

Grinder The device used to grind coffee beans before brewing. For espresso, a burr grinder is essential — blade grinders produce inconsistent particle sizes. Conical burr and flat burr are the two main types. → Best Espresso Grinders

Group Head The part of the espresso machine where the portafilter locks in. Water flows through the group head to brew the espresso. Group head temperature is critical for extraction quality.

H

HX (Heat Exchanger) A machine design with a single boiler that uses a heat exchanger coil to produce steam and brew water simultaneously. Allows steaming and brewing without switching modes, unlike single-boiler machines. Popular in mid-range prosumer machines.

Head Space The gap between the top of the tamped coffee puck and the shower screen of the group head. Too little head space causes the puck to contact the screen; too much can affect pre-infusion. Typically 5-7mm.

I

Infusion The initial wetting of the coffee puck before full pressure extraction begins. Also called pre-infusion. Helps even water distribution before high pressure hits the puck.

L

Latte (Caffè Latte) Italian for “milk coffee.” Espresso + steamed milk in roughly 1:3-1:4 ratio, topped with a thin layer of microfoam. The most popular espresso drink globally. The milk dominates the flavor. → Full guide

Latte Art Patterns created in the surface of a latte by pouring steamed milk in a specific way. Common designs: heart, rosette, tulip. Requires well-made microfoam and practice. Latte art is a byproduct of good milk steaming technique, not an end in itself.

Lungo Italian for “long.” A lungo is an espresso pulled with more water than a standard shot — roughly 80-100ml instead of 25-35ml. More bitter and less concentrated than a standard espresso, but not the same as an Americano (lungo uses the same extraction method; Americano adds hot water after). → Full guide

M

Macchiato (Espresso Macchiato) Italian for “stained” or “marked.” An espresso shot with a small amount of milk foam on top — the milk marks the espresso. One of the smallest, strongest milk-based espresso drinks. Not to be confused with the much larger, sweeter Starbucks-style latte macchiato. → Full guide

Microfoam Milk that has been steamed to have very small, uniformly sized bubbles — creating a smooth, velvety texture that looks and pours like wet paint. Essential for latte art and for integrating smoothly with espresso. Distinct from stiff foam (large bubbles).

Moka Pot An Italian stovetop coffee maker that produces strong, concentrated coffee using steam pressure. Not a true espresso machine (only 1-2 bars of pressure vs. 9 bars for espresso) but produces coffee with a similar intensity. Popular as an espresso alternative. → Moka Pot vs Espresso Machine

P

Puck The disk of compressed coffee grounds in the portafilter basket after tamping. A well-formed puck should be flat, level, and firm. After extraction, a spent puck should hold its shape and be relatively dry.

Portafilter The handle-mounted basket assembly that locks into the group head. Holds the filter basket and ground coffee. A naked or bottomless portafilter has no spout and allows observation of extraction flow.

Pre-Infusion A phase at the start of extraction where low pressure water gently wets the coffee puck before full extraction pressure is applied. Promotes even saturation and reduces channeling. Some machines have adjustable pre-infusion.

R

Ristretto Italian for “restricted.” A ristretto is a shorter, more concentrated espresso — typically a 1:1 ratio (same dose, half the yield). Higher extraction of early-stage sweetness, less bitterness. More syrupy and intense than a standard espresso. The building block of many specialty drinks. → Full guide

Roast Level How long and at what temperature coffee beans are roasted. Light roast: higher acidity, more origin flavor, more caffeine by mass. Medium roast: balanced. Dark roast: lower acidity, more bitterness, more body, less caffeine by mass. Most espresso blends are medium-dark to dark.

S

Shot A single serving of espresso. A single shot is about 25-35ml; a double shot (doppio) is about 60ml. Most café drinks are built on double shots.

Single Origin Coffee beans sourced from a specific country, region, or farm — as opposed to a blend of beans from multiple origins. Single origin espressos tend to have more distinctive, traceable flavor profiles.

Solenoid Valve A valve in espresso machines that releases residual pressure from the group head after extraction. The “click” or hiss you hear when you release the portafilter. Allows the puck to de-pressurize cleanly rather than dripping.

Spro Slang for espresso, used in specialty coffee communities.

T

Tamping Pressing the coffee grounds in the filter basket into a flat, level puck using a tamper. Standard tamping pressure: 15-20kg. The goal is a level surface, not a specific force. Uneven tamping causes channeling. → Getting started guide

TDS (Total Dissolved Solids) A measurement of how much coffee has dissolved into the brew, expressed as a percentage. Measured with a refractometer. Espresso TDS: typically 8-12%. Used alongside extraction yield to characterize a shot precisely.

Temperature Surfing A technique for single-boiler machines where the user triggers the brew cycle (or flush) immediately after steaming to bring the boiler temperature down to the correct brew temperature. Required on machines without dedicated brew temperature control.

Thermoblock A heating element design used in entry-level espresso machines. Water passes through a small, thin metal block that heats quickly. Fast to heat up but less temperature stable than a full boiler. Found in many entry-level machines.

U

Under-Extraction When too little of the coffee’s soluble compounds are dissolved. Tastes sour, weak, and thin. Causes: grind too coarse, too little dose, too short extraction time, water too cold.

V

VST Baskets High-precision filter baskets made by VST (Vermont Specialty Tools) with consistent, precisely sized perforations. Popular with serious home baristas for improving shot consistency over stock OEM baskets.

W

WDT (Weiss Distribution Technique) A method of distributing ground coffee in the basket using a thin needle or wire to break up clumps and distribute grounds evenly before tamping. Named after John Weiss. Reduces channeling. A WDT tool is a thin metal stick with fine needles.

Water Hardness The mineral content of water used for espresso. Hard water (high calcium/magnesium) can improve extraction flavor but causes scale buildup. Soft water reduces scaling but can taste flat. Target for espresso: 50-150ppm total dissolved minerals. → Full guide

Y

Yield The weight (in grams) of liquid espresso in the cup. Part of the espresso ratio: dose in → yield out. Measured by placing the cup on a scale. Hitting a consistent yield is one of the most important variables for repeatable espresso. → Espresso ratio guide