Reference
Coffee Glossary
A plain-English reference for the terms that show up across our articles — from bean varieties and processing methods to brewing science, espresso drinks, chemistry, and the health-and-physiology vocabulary. Where a term has a dedicated article, we link to it. 58 terms across 9 categories.
Beans & Cultivation
6 terms
Beans & Cultivation
- Arabica
- The species Coffea arabica, accounting for roughly 60–70% of global coffee production. Grows at higher altitudes (600–2200 m), tastes sweeter and more complex than robusta, and contains about half the caffeine per bean.Full article →World Coffee Research variety catalog ↗
- Robusta
- The species Coffea canephora. Hardier and higher-yielding than arabica, grown at lower altitudes, with roughly twice the caffeine and a heavier, more bitter cup. Common in espresso blends and instant coffee.Full article →
- Coffee cherry
- The fruit of the coffee tree. Each cherry usually contains two seeds (coffee beans) surrounded by pulp, mucilage, and parchment. Ripe cherries are typically deep red, though some varieties ripen yellow.Full article →
- Parchment
- The thin, papery hull surrounding the coffee bean inside the cherry. Removed during hulling, and the green beans are often shipped and stored with parchment still on until export.
- Silverskin
- The last thin membrane clinging to the coffee bean after hulling. Flakes off during roasting as chaff and is separated by roaster airflow.
- Cultivar / Variety
- A distinct genetic line within a coffee species. Well-known cultivars include Typica, Bourbon, Caturra, Catuai, SL28, SL34, and Geisha. Varieties matter for flavour, disease resistance, and yield.WCR interactive variety catalog ↗
Processing
5 terms
Processing
- Washed process
- Coffee cherries are depulped, the beans are fermented in water for 12–72 hours to remove mucilage, then washed and dried. Produces clean, bright cups where variety and terroir come through clearly.Full article →
- Natural (dry) process
- Whole coffee cherries are dried in the sun on raised beds or patios for weeks. The bean absorbs sugars from the fruit, producing intensely fruity, wine-like cups. Common in Ethiopia and Brazil.Full article →
- Honey process
- A hybrid where cherries are depulped but the sticky mucilage is left on the beans during drying. Named for the honey-like appearance of the sticky beans, not for any honey ingredient. Yields sweet, syrupy cups.Full article →
- Anaerobic fermentation
- Cherries or depulped beans are fermented in sealed tanks with limited oxygen, sometimes with added yeasts. Produces unusually intense fruit and fermented flavour notes that some drinkers love and others dislike.Full article →
- Cascara
- The dried skin (husk) of the coffee cherry, brewed as a tea-like beverage. Naturally sweet, fruity, and lower in caffeine than coffee. Sold as a specialty beverage in its own right.Full article →
Roasting
5 terms
Roasting
- First crack
- The audible popping sound around 196°C during roasting, when steam pressure ruptures cell walls. Beans have reached the light-roast stage. The end of first crack marks the classic City roast level.Full article →
- Second crack
- A quieter, sharper crackling around 224°C, when bean oils are forced to the surface. Signals the transition into dark-roast territory. Beyond second crack is French or Italian roast.Full article →
- Development time
- The interval between first crack and drop (end of roast). Longer development builds sweetness and body; shorter development preserves acidity and origin character. A key control lever for the roaster.Full article →
- Maillard reaction
- The chemical reaction between amino acids and reducing sugars at 160–200°C that produces most of coffee's aromatic compounds and characteristic brown colour. Runs in parallel with caramelisation during roasting.Full article →
- Roast level
- How far the roast has progressed, expressed as light, medium, medium-dark, or dark. Also called by traditional names: Cinnamon, City, Full City, Vienna, French, Italian.Full article →
Brewing
8 terms
Brewing
- Extraction yield
- The percentage of the coffee's soluble mass that ended up in the cup. The Specialty Coffee Association's golden-cup target is 18–22%. Below is under-extracted (sour); above is over-extracted (bitter).Full article →
- Total dissolved solids
- The concentration of coffee solids in the finished brew, measured as a percentage by weight. Filter coffee typically sits at 1.2–1.4% TDS; espresso is 8–12%. Measured with a refractometer.Full article →
- Golden cup
- The Specialty Coffee Association's target range for well-brewed coffee: 1.15–1.35% TDS strength and 18–22% extraction yield. Both dimensions matter and can be controlled independently.Full article →SCA coffee standards ↗
- Grind size
- How finely coffee is ground, measured in microns or by feel. Finer grinds increase surface area and extract faster. Espresso needs fine grind, cold brew needs coarse; every method has its window.Full article →
- Bloom
- The initial 30–45 second wet with 2× the coffee's weight in water, letting trapped CO₂ escape before the main pour. Improves extraction evenness. Freshly roasted coffee blooms more.Full article →
- Brew ratio
- The mass ratio of coffee to water, expressed like 1:16. Most filter methods sit between 1:15 and 1:18; espresso is around 1:2 (18 g coffee → 36 g espresso).Full article →
- Pre-infusion
- A gentle initial wetting of the grounds at low pressure (in espresso) or the bloom phase (in filter). Reduces channeling and improves extraction evenness.
- Channelling
- When water finds a low-resistance path through the coffee bed, extracting some grounds too much and others too little. Usually caused by uneven grind, poor tamp, or fines migration.
aka Extraction %, EY
aka TDS, Brew strength
Chemistry & Compounds
6 terms
Chemistry & Compounds
- Caffeine
- The primary stimulant in coffee (1,3,7-trimethylxanthine). Works by blocking adenosine receptors in the brain, reducing perceived tiredness. Typical drip cup contains 80–100 mg.Full article →
- Chlorogenic acids
- The dominant polyphenol class in coffee, 5–8% of green arabica by weight. Heat-sensitive: falls sharply during roasting. Coffee is the largest dietary source of chlorogenic acids in most Western diets.Full article →
- Melanoidins
- Brown-pigment compounds formed by Maillard browning during roasting. Contribute much of dark-roast coffee's antioxidant activity and its darker cup colour and body.Full article →
- Cafestol & kahweol
- Coffee diterpenes (oils) that raise LDL cholesterol when consumed in unfiltered coffee (French press, espresso, moka pot, Turkish). Paper filters remove nearly all of them.Full article →
- Trigonelline
- An alkaloid in green coffee that partially breaks down during roasting to form nicotinic acid (niacin) and various aromatic compounds. Contributes bitterness and B-vitamin content.
- Acrylamide
- A trace compound formed in coffee (and many other cooked foods) during roasting. Levels are highest in light roasts and decline with longer roasting. Well below regulatory concern thresholds in a typical cup.FDA acrylamide Q&A ↗
aka CGAs
Espresso Drinks
9 terms
Espresso Drinks
- Espresso
- A ~30 mL shot pulled by forcing 90°C water through fine-ground coffee at 9 bars of pressure over 25–30 seconds. Distinctively concentrated (8–12% TDS) with an emulsified crema on top.Full article →
- Ristretto
- A short espresso shot using the same coffee dose but less water — roughly 1:1 in vs out. More concentrated, less bitter, less caffeine than a standard shot.Full article →
- Lungo
- A long espresso shot using more water for the same coffee dose — roughly 1:3 or longer. Pulls more of the bitter, dry compounds. More total volume and caffeine.Full article →
- Crema
- The reddish-brown foam that sits on top of a fresh espresso shot. An emulsion of CO₂, coffee oils, and dissolved solids. Presence and colour are weak indicators of shot quality.Full article →
- Cappuccino
- An Italian espresso drink: one espresso shot topped with equal parts steamed milk and thick milk foam, in a small 5–6 oz cup.Full article →
- Latte
- Espresso combined with a larger volume of steamed milk (typically 8–16 oz) topped with a thin layer of microfoam. Latte art is drawn into the foam.Full article →
- Flat white
- Australian/New Zealand drink: double espresso topped with silky microfoam in a small 5–6 oz cup. More espresso-forward than a latte.Full article →
- Macchiato
- 'Marked' in Italian. Traditionally an espresso with a small dollop of foamed milk. Not to be confused with the milk-forward Starbucks caramel macchiato.Full article →
- Americano
- Espresso diluted with hot water to filter-coffee strength. Origin story links it to WWII US servicemen in Italy diluting espresso.Full article →
Equipment
7 terms
Equipment
- Burr grinder
- A grinder that crushes coffee between two abrasive plates, producing consistent particle sizes. Vastly better than blade grinders for extraction consistency. Conical and flat burr geometries exist.Full article →
- Portafilter
- The handled basket that clamps into an espresso machine's group head and holds the coffee puck during extraction.
- Group head
- The espresso machine component where the portafilter locks in and water is delivered to the coffee at pressure.
- V60
- Hario's iconic conical pour-over dripper with spiral internal ribs and a large single hole. Encourages fast, clean brews and rewards precise technique.Full article →
- Chemex
- Peter Schlumbohm's 1941 hourglass-shaped pour-over vessel with unusually thick bonded paper filters. Produces exceptionally clean cups with almost no sediment or oils.Full article →
- AeroPress
- Alan Adler's 2005 immersion-then-press brewer using a plunger to force brewed coffee through a paper (or metal) filter. Versatile, forgiving, and travel-friendly.Full article →
- Moka pot
- Alfonso Bialetti's 1933 stovetop brewer that forces steam-pressure-driven water up through a coffee bed. Produces strong, espresso-adjacent coffee but not true espresso (no crema, lower pressure).Full article →
Culture & Industry
6 terms
Culture & Industry
- Third wave coffee
- The movement (mid-2000s onward) that treats coffee as an artisanal product with traceable origins, lighter roasts, and specialty preparation. Contrasts with the 'second wave' Starbucks-era café culture.Full article →
- Specialty coffee
- Coffee scoring 80+ on the 100-point SCA cupping scale. The specialty designation covers both quality and traceability standards through the supply chain.Specialty Coffee Association ↗
- Single origin
- Coffee from a single geographic source — a country, region, farm, or lot. Contrasts with blends. The specificity varies enormously; 'single origin Ethiopia' says less than 'single farm, single lot.'Full article →
- Cupping
- The standardised method for evaluating coffee quality: freshly ground coffee is steeped in hot water, the crust is broken, and evaluators score aroma, flavour, body, aftertaste, and defects.SCA cupping protocol ↗
- Q-grader
- A licensed evaluator certified by the Coffee Quality Institute to score arabica coffee against the specialty grading standard. Considered the gold standard credential in coffee tasting.Coffee Quality Institute ↗
- Fair Trade / Direct Trade
- Fair Trade is a certification with minimum price and social standards. Direct Trade is a bilateral relationship (roaster ↔ producer) with negotiated prices, no formal certification. Both aim to improve producer economics.
Health & Physiology
6 terms
Health & Physiology
- Adenosine
- A neurotransmitter that builds up during waking hours and signals sleepiness by binding to A1 and A2A receptors. Caffeine is an antagonist — it blocks these receptors, preventing the sleepiness signal.Full article →
- Caffeine half-life
- The time for the body to clear half of a caffeine dose. Averages ~5 hours in healthy adults but varies from 2–3 hours (fast metabolisers) to 8+ hours (slow, pregnant, or on oral contraceptives).Full article →
- CYP1A2
- The liver enzyme that metabolises about 95% of ingested caffeine. Genetic variants (fast vs slow variants) explain much of the individual variation in how coffee affects people.Full article →
- ADORA2A
- The gene encoding the adenosine A2A receptor. Certain variants make carriers more sensitive to caffeine's anxiogenic and sleep-disrupting effects, independent of metabolism.Full article →
- Caffeine dependence
- Physical adaptation to regular caffeine intake, producing withdrawal symptoms (headache, fatigue, difficulty concentrating) if stopped abruptly. Distinct from addiction, which requires behavioural harm.Full article →
- Gastrocolic reflex
- The colonic muscular response triggered by food or drink entering the stomach. Coffee is a particularly potent trigger — one reason many people experience a bowel urge shortly after drinking it.Full article →
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