Coffee Glossary: Every Term You Need to Know

Coffee has its own language. Walk into a specialty shop or browse a barista forum and you'll hear words like "channeling," "bloom," and "WDT" thrown around like everyone just knows. Nobody was born knowing this stuff.

This glossary covers every term you'll encounter as a home barista. No jargon-for-the-sake-of-jargon — just clear explanations.

Brewing Terms

Bloom — The initial pour of hot water over fresh grounds. CO2 escapes and the coffee puffs up. Essential for pour over to ensure even extraction.

Brew ratio — The relationship between coffee and water by weight. Written as 1:X. Typical ratios: espresso 1:2, pour over 1:15 to 1:17, cold brew 1:5.

Bypass — Water that flows around the coffee bed without extracting flavor. Common in pour over when water runs down the sides of the filter.

Channeling — When water finds a path of least resistance through the coffee bed, creating uneven extraction. Common in espresso with poor puck prep.

Drawdown — The final phase of a pour over where water drains through the bed. Fast = coarse grind; slow = fine grind.

Extraction — Dissolving flavor compounds from grounds into water. Under-extraction = sour and thin. Over-extraction = bitter and harsh. Sweet spot: 18-22%.

Immersion brewing — Methods where grounds sit in water for a set time (French press, AeroPress, cold brew). Opposite of percolation.

Percolation — Methods where water flows through a bed of grounds (pour over, drip). Produces a cleaner cup than immersion.

TDS (Total Dissolved Solids) — How much coffee is dissolved in your cup. Measured with a refractometer. Higher TDS = stronger. Not the same as "better."

Espresso Terms

Crema — The golden-brown foam on top of a fresh shot. Created by CO2 under pressure. Looks impressive but doesn't tell you much about taste.

Dial in — Adjusting your grinder for the right extraction. See our full guide: Espresso Grind Size Explained.

Dose — Weight of ground coffee in the portafilter. Standard double shot: 18g (range: 14-20g).

Grouphead — The part of the machine where the portafilter locks in. Water flows from the boiler through here into the puck.

Naked portafilter (bottomless) — Portafilter with the bottom cut off to see the extraction. Great for diagnosing channeling.

Portafilter — The handle-and-basket that holds the ground coffee. Locks into the grouphead to brew.

Pre-infusion — Low-pressure soak of the puck before full pressure. Reduces channeling, more even extraction.

Pressure profiling — Varying water pressure during a shot (instead of constant 9 bars). Some machines let you control the curve.

Puck prep — Everything before pulling: dosing, distributing, tamping. Good prep = even extraction = better espresso.

Pull a shot — Brewing espresso. From old lever machines where you literally pulled a lever.

Tamping — Pressing grounds flat in the portafilter. About 30 lbs of pressure, keep it level.

WDT (Weiss Distribution Technique) — Using a thin needle to stir and break up clumps before tamping. Dramatically improves extraction. Named after John Weiss.

Yield — Weight of liquid espresso in the cup. Standard double: 36g from 18g dose (1:2).

Grinder Terms

Burrs — Cutting surfaces inside a grinder. Flat burrs: uniform particles, clean flavors. Conical: more body, some fines. Quality matters more than type.

Fines — Very small particles from grinding. Some inevitable, too many = over-extraction and muddiness. Cheap grinders produce more.

Grind retention — Coffee stuck inside the grinder between uses. Old retained grounds go stale. Lower retention = better.

Single-dose grinder — Designed to grind exactly what you put in, minimal retention. Weigh beans, drop in, grind all out.

Stepless vs. stepped — Stepped: fixed click positions. Stepless: infinite adjustment. Stepless preferred for espresso.

Roasting Terms

First crack — Audible popping during roasting. Beans expand and release moisture. Light roasts stop shortly after.

Second crack — Quieter cracking, deeper in. Dark roasts reach second crack. Oils migrate to surface.

Light roast — More acidity, more origin character, fruity/floral. Higher caffeine.

Medium roast — Balanced. Some origin character plus caramel and chocolate from roasting.

Dark roast — Bold, smoky, low acidity. Origin character mostly replaced by roast flavor. Oily surface.

Single origin — Coffee from one farm, region, or country. Highlights unique flavor characteristics.

Blend — Coffee mixed from multiple origins for consistency. Most espresso blends use 2-4 origins.

Milk & Drink Terms

Microfoam — Silky steamed milk with tiny, uniform bubbles. Essential for latte art.

Latte — Espresso + steamed milk. 1-2 shots with 8-12oz steamed milk, thin foam layer.

Cappuccino — Espresso + steamed milk + foam. More foam, less milk than a latte.

Flat white — Like a latte but less milk, thinner microfoam. More espresso flavor comes through.

Americano — Espresso + hot water. Volume like drip coffee, with espresso's flavor.

Cortado — Equal parts espresso and steamed milk (~4oz total). Small, balanced, strong.