Glossary

Homebrew Glossary

A 

ABV (Alcohol by Volume) — The percentage of alcohol in the finished beer by volume. Calculated from original and final gravity readings. 

Adjunct — Any fermentable ingredient other than malted barley (e.g., corn, rice, oats, wheat, sugar, honey). 

Aeration — Introducing oxygen into cooled wort before pitching yeast to support healthy yeast growth. 

Airlock (Fermentation Lock) — A one-way valve on a fermenter that lets CO₂ escape while blocking air and contaminants. 

Ale — Beer fermented with top-fermenting yeast (*Saccharomyces cerevisiae*) at warmer temperatures (typically 60–72°F / 15–22°C). 

All-Grain Brewing — Brewing method that extracts fermentable sugars entirely from malted grains via mashing (as opposed to using malt extract). 

Alpha Acid — Bittering compounds in hops; the percentage on hop packaging indicates potential bitterness. 

Attenuation — The percentage of sugars in the wort that yeast converts into alcohol and CO₂. Higher attenuation yields a drier beer.

B 

Barley — The primary grain used in brewing; malted barley provides the majority of fermentable sugars and enzymes. 

Bitterness / IBU — See IBU. 

Boil — The stage after mashing where wort is boiled (usually 60–90 minutes) to sterilize, concentrate, isomerize hop alpha acids, and drive off unwanted compounds. 

Bottle Conditioning — Carbonating beer in the bottle by adding priming sugar so residual yeast produces CO₂. 

Body — The perceived fullness or mouthfeel of the beer (light, medium, or full). 

Brettanomyces (“Brett”) — A wild yeast genus that can produce funky, earthy, or sour flavors; used intentionally in some styles or as a contaminant.

C 

Carboy — A large glass or plastic vessel (typically 5–6.5 gallons) used for fermentation. 

Cold Break — Proteins and other compounds that precipitate out of wort when it is rapidly cooled after the boil. 

Conditioning — The period after primary fermentation when beer matures, clears, and develops flavor (can include bottle or keg conditioning). 

Conversion — The enzymatic process during mashing that turns starches into fermentable sugars.

D 

Diacetyl — A fermentation byproduct that tastes like butter or butterscotch; usually undesirable in most styles (yeast can reabsorb it during a diacetyl rest). 

DME (Dry Malt Extract) — Powdered concentrated malt sugars used in extract brewing. 

Dry Hopping — Adding hops after fermentation (or late in the process) primarily for aroma and flavor without much additional bitterness.

E 

Ester — Fruity aroma and flavor compounds produced by yeast during fermentation (e.g., banana, apple, pear notes). 

Extract Brewing — Brewing method that uses malt extract (liquid or dry) as the primary source of fermentable sugars instead of mashing grains.

F 

Fermentation — The process in which yeast converts sugars into alcohol and carbon dioxide. 

Final Gravity (FG) — The specific gravity of the beer after fermentation is complete; indicates residual sugars. 

Flocculation — The tendency of yeast cells to clump together and settle out of the beer after fermentation.

G 

Gravity — Short for specific gravity; a measure of the density of wort or beer relative to water (indicates sugar content). 

Grist — The crushed malt and other grains prepared for mashing.

H 

Hops — The flowers (cones) of the *Humulus lupulus* plant used for bitterness, flavor, aroma, and preservation. 

Hot Break — Proteins that coagulate and precipitate during the boil. 

Hydrometer — An instrument used to measure the specific gravity of wort or beer.

I 

IBU (International Bitterness Units) — A scale measuring the concentration of isomerized alpha acids (bitterness) in beer. Higher numbers generally mean more bitterness. 

Isomerization — The chemical change of hop alpha acids during the boil that creates soluble bitter compounds.

K 

Kettle — The vessel used for boiling the wort (brew kettle). 

Krausen — The foamy head of yeast and proteins that forms on top of fermenting beer.

L 

Lager — Beer fermented with bottom-fermenting yeast (*Saccharomyces pastorianus*) at cooler temperatures and typically lagered (cold-conditioned) for an extended period. 

Lautering — The process of separating sweet wort from the grain bed after mashing. 

LME (Liquid Malt Extract) — Thick syrup of concentrated malt sugars used in extract brewing.

M 

Malt / Malted Barley — Barley that has been steeped, germinated, and dried (kilned) to develop enzymes and convert starches. 

Mash — The mixture of crushed grains and hot water in which enzymes convert starches to sugars. 

Mouthfeel — The tactile sensations of the beer in the mouth (body, carbonation, astringency, creaminess, etc.).

O 

Original Gravity (OG) — The specific gravity of the wort before fermentation begins; indicates the potential alcohol and body. 

Oxidation — Exposure of beer to oxygen after fermentation, which can create stale, cardboard, or sherry-like off-flavors.

P 

Pitching — Adding yeast to the cooled wort to start fermentation. 

Priming — Adding a measured amount of sugar (or other fermentable) before bottling or kegging to create carbonation. 

pH — A measure of acidity/alkalinity; important for mash efficiency and beer stability (typical mash pH target is around 5.2–5.6).

R 

Racking — Transferring beer from one vessel to another (e.g., primary to secondary fermenter or to a bottling bucket), usually to leave sediment behind. 

Recirculation (Vorlauf) — Circulating wort through the grain bed at the start of lautering to set the filter bed and clarify the runoff.

S 

Sanitization — Reducing microorganisms on equipment to safe levels (distinct from sterilization). Critical for preventing infection. 

Sparge — Rinsing the grain bed with hot water after mashing to extract remaining sugars. 

Specific Gravity (SG) — The density of a liquid compared to water; used to track sugar content before and after fermentation. 

SRM (Standard Reference Method) — A scale for measuring beer color (lower = paler, higher = darker). 

Starter — A small volume of wort used to grow a larger, healthier yeast population before pitching into the main batch.

T 

Trub — The sediment of proteins, hop material, and other solids that settles during and after the boil and fermentation.

W 

Whirlpool — Creating a circular current in the kettle after the boil to collect hop and trub material in the center for clearer wort transfer. 

Wort — The sweet, unfermented liquid extracted from the mash that becomes beer after fermentation.

Y 

Yeast — The single-celled fungus that ferments sugars into alcohol and CO₂. Ale yeasts and lager yeasts are the primary types used.

Z 

Zymurgy — The science and study of fermentation, especially as applied to brewing.