Every coffee word this site uses, in plain language, with a link to where it matters. The terms are grouped by topic and listed alphabetically within each group.
Brewing
Agitation
Movement caused by pouring, stirring, swirling, or plunging. More agitation usually speeds up extraction, which is why recipes say exactly when to stir and when to leave the coffee alone.
Bloom
The first small pour in a pourover or phin recipe. It wets the grounds and lets trapped carbon dioxide escape before the main pour. The word also describes what fresh grounds do when hot water first hits them: they puff up and bubble. Stale coffee barely blooms; see how to tell if coffee is stale.
Body
How heavy, creamy, or tea-like the coffee feels in your mouth. Metal filters and immersion brewers give more body; paper filters give less.
Brew ratio
Coffee compared with water by weight. A 1:16 ratio uses 1g of coffee for every 16g of water. The lower the second number, the stronger the cup. See how much coffee per cup or the brew ratio calculator.
Bypass water
Water that reaches the cup without passing through the grounds, either added on purpose after brewing, as in an Americano, or by accident, when water runs down the filter wall. It changes strength, not extraction. See bypass water.
Channeling
Water finding a few easy paths through the coffee instead of flowing evenly, so some grounds over-extract while others barely brew. On espresso it is the usual cause of a shot that tastes sour and bitter at once, or that sprays and turns pale early; see fixing channeling.
Concentrate
Coffee brewed deliberately strong, to be diluted with water, milk, or ice. Cold brew, the AeroPress top-up method, and espresso-based drinks all start with one.
Contact time
How long water and coffee spend together. Longer contact extracts more. The grind guide lists a typical contact time for each method.
Dose
The weight of dry coffee in a brew. “An 18g dose” means 18g of ground coffee. On espresso, the basket sets the dose; see scaling the dose.
Drawdown
The time water takes to drain through a pourover after the final pour.
Extraction
Flavor dissolving from coffee into water. Under-extracted coffee has not had enough dissolved out of it and tastes sour, sharp, and thin. Over-extracted coffee has had too much pulled out and tastes bitter, hollow, and drying. Grind is the main dial; see calibrating the grind, or extraction, explained for the whole picture.
Immersion
Brewing where the coffee sits in the water for the whole brew, as in a French press, cold brew, or AeroPress, rather than water passing through a bed of coffee, as in pourover and drip. Immersion is the more forgiving of the two, because pouring technique matters less.
Inverted method
An AeroPress technique that stands the brewer upside down so no coffee drips through while it steeps. See the inverted method, including the safety note.
Strength
How concentrated the coffee is. Strength is set mainly by the brew ratio, and it is separate from extraction: a cup can be strong and sour, or weak but perfectly balanced. Telling the two apart is most of troubleshooting; see weak versus sour.
TDS
Total dissolved solids. In water, it measures how much is dissolved but not which minerals; see water for coffee. In brewed coffee, specialized meters use it to measure strength.
Espresso and milk
Crema
The layer of fine, tan foam on top of an espresso shot, made of gas and oils forced out under pressure. Fresh coffee makes more of it. Thick crema from a pressurized basket is mostly trapped air, so it says little about the shot.
Group head
The part of an espresso machine that the portafilter locks into, where the hot water comes out.
Latte, cappuccino, flat white, and cortado
Espresso and milk in different proportions. A latte has the most milk; a cappuccino has less milk and more foam; a flat white has less milk, a double shot, and a thin, velvety foam; a cortado is roughly equal parts espresso and warm milk. See the full comparison.
Lungo
A long espresso, pulled to a ratio of 1:3 or more. It tastes lighter and more transparent than a standard shot. See espresso ratios.
Portafilter
The handle on an espresso machine that holds the basket of grounds and locks into the group head. “Lock in the portafilter” means attach it and start the shot.
Pressurized basket
An espresso basket with a double wall and a single small exit hole, common on entry-level machines. It builds pressure for you, which makes it forgiving, but it also means changing the grind barely changes the shot. See pressurized baskets.
Puck
The disk of grounds tamped into an espresso basket, and the word for what is left in it after the shot. A puck with clumps or an uneven surface is what causes channeling.
Ristretto
A short espresso, stopped at a ratio of about 1:1 to 1:1.5. It is heavier and sweeter than a standard shot, and especially good in milk drinks.
Tamp
Pressing the ground coffee in an espresso basket into a flat, even bed. A level tamp matters more than a hard one.
Yield
The weight of liquid espresso in the cup. An 18g dose pulled to a 36g yield is a 1:2 ratio. Yield changes a shot’s strength rather than its extraction; see how to dial in espresso.
Beans and roasting
Arabica
The species most of the world’s coffee comes from, including almost all specialty coffee. It has more sweetness and acidity than robusta, and less caffeine. See arabica vs robusta.
Blend
Coffees from more than one origin, combined for a balanced flavor that stays the same from season to season. Many espresso coffees are blends.
Cafestol
A compound in coffee oil that raises cholesterol. Paper filters hold most of it back; metal filters, such as a French press or espresso basket, let it through. See filtered vs unfiltered coffee.
Decaf
Coffee with most of its caffeine removed from the green beans before roasting. It is not caffeine-free: a typical 8-ounce cup has about 2 to 15mg, against about 96mg in a regular cup. See is decaf coffee really caffeine-free.
Degassing
Freshly roasted coffee giving off carbon dioxide, which it does for days after roasting. The one-way valve on a coffee bag lets the gas out without letting air in. Brewed too soon, very fresh coffee can taste sharp or uneven; see coffee can be too fresh.
Processing
What happens to the coffee cherry after it is picked. Washed coffee has the fruit removed before drying and tastes clean and bright; natural coffee dries inside the whole cherry and tastes heavy and fruity; honey process sits in between. See processing.
Roast date
The day the coffee was roasted, printed on bags from specialty roasters. It tells you far more about freshness than a best-by date; see how long coffee stays fresh.
Roast level
How long and how dark the beans were roasted. Light roasts taste of fruit and flowers, dark roasts of cocoa and toast, and medium roasts sit in between. See roast level.
Robusta
The other major coffee species. It is hardier and cheaper to grow, tastes more bitter and earthy, and carries around one and a half to two times the caffeine of arabica. It dominates Vietnamese coffee and turns up in some espresso blends; see arabica vs robusta and which coffee has the most caffeine.
Single origin
Coffee from one place, such as a single country, region, or farm, sold so that the character of that place shows. Pourover is the best method for tasting it.
Grinding
Blade grinder
A grinder with a spinning blade that chops the beans rather than grinding them, leaving a mix of boulders and fines. You can still brew well with one; see grinders, briefly.
Boulders
Oversized chunks in a grind. They under-extract while the fines around them over-extract, so a grind with many of both tastes sour and bitter at the same time.
Burr grinder
A grinder that crushes beans between two burrs set a fixed distance apart, producing much more even particles than a blade grinder. It is the upgrade that improves every method at once.
Fines
Dust-sized particles in any grind. They extract quickly, slow the flow of water, and slip through metal filters as sediment. Every grinder makes some; cheap grinders make the most.
Grind size
How fine or coarse the coffee is ground, from extra fine like powdered sugar to extra coarse like cracked peppercorns. See the grind scale.
Water
Alkalinity
Water’s ability to neutralize acid, mostly from bicarbonate. A little keeps coffee balanced; too much makes it taste flat and dull. See what the minerals do.
Hardness
The calcium and magnesium dissolved in water. They help extract flavor, but very hard water makes coffee taste chalky and leaves scale.
Scale
The chalky white mineral deposit that hard water leaves inside kettles and coffee machines. It slows brewing and stops machines heating properly. Descaling dissolves it; see keeping a drip machine clean.
Brewers and gear
Cezve
The small, long-handled pot used for Turkish coffee, often sold as an ibrik.
Gooseneck kettle
A kettle with a long, thin spout for a slow, steady pour. It genuinely helps with pourover and makes little difference to other methods.
Moka pot
A stovetop brewer often sold as a stovetop espresso maker. It makes strong, rich coffee, but not espresso, because it works at a fraction of the pressure. See how to brew with a Moka Pot.
Phin
The small metal filter used for Vietnamese coffee. It sits on top of the cup and drips strong coffee straight into it.
Common questions
Do I need a scale?
No, but a scale makes a good brew repeatable and turns troubleshooting into something more useful than guessing.
Is a burr grinder worth it?
A burr grinder produces more even particles than a blade grinder. That generally makes extraction more even, but you can still improve coffee by measuring carefully and keeping a blade grinder clean. For where it fits among your first purchases, see what to buy for your first coffee setup.
Why does my coffee taste sour?
It is often under-extracted. Start by grinding finer. See the troubleshooting guide for the full decision path.
Can I use boiling water?
Boiling water is not automatically harmful, especially for light roasts, but slightly cooler water may taste better with darker coffee. Start with the method guide’s temperature and adjust by taste. See water temperature for coffee for the full answer.
How much coffee should I use?
For filter coffee, 1:15 to 1:17 is a useful starting range: about 3 level tablespoons for an 8-ounce cup. See how much coffee per cup for every cup size, or use the brew ratio calculator for exact amounts.
How long does coffee stay fresh?
Whole beans taste best from a few days to about a month after roasting, and within about two weeks of opening the bag. Ground coffee fades faster. See how long coffee stays fresh.
Is tap water good enough for coffee?
If it tastes clean at room temperature, yes. If it smells of chlorine, tastes off, or leaves heavy scale in the kettle, see what water is best for coffee.
Does espresso have more caffeine than drip coffee?
Per ounce, yes. Per cup, no: a single shot has about 63mg of caffeine and an 8-ounce cup of brewed coffee about 96mg, and even a double only about matches a full mug. See which coffee has the most caffeine.