A

ABV (Alcohol by Volume)

The percentage of alcohol in beer by volume. Higher ABV generally means more fermentable sugars were converted into alcohol.

Adjunct

Any fermentable ingredient added to the mash or boil besides malted barley – like corn, rice, sugar, honey, or unmalted grains.

Aeration

Introducing oxygen into cooled wort before fermentation. Yeast need oxygen early to build healthy cell membranes.

Alpha acids

Compounds in hops that become bitter when boiled (isomerized). Often shown as a percent on hop packaging.

Amylase

Enzymes in malt that convert starch into sugars during the mash. The two common types are alpha-amylase and beta-amylase.

Attenuation

How much of the wort sugars yeast consume. Higher attenuation usually means a drier beer and lower final gravity.

Autolysis

When yeast cells break down and release compounds that can taste meaty, rubbery, or soy-like. More common with stressed yeast or long warm contact.

B

Backsweeten

Adding sweetness after fermentation (usually for cider, mead, or some specialty beers). Requires stabilization if you want to avoid renewed fermentation.

Ball lock

A common keg quick-disconnect style. Uses separate gas and liquid posts with ball-bearing connectors.

Barleywine

A strong ale style with high gravity and rich malt character. Often benefits from aging.

Batch sparge

Sparging by adding hot water to the mash tun in one or more batches, stirring, then draining.

Beta-glucans

Gummy compounds found in grains like oats and rye that can thicken the mash and slow runoff. A beta-glucan rest can help.

BIAB (Brew in a Bag)

An all-grain method where grain is mashed in a mesh bag inside the kettle, then lifted to drain.

Bittering addition

Hops added early in the boil to contribute bitterness more than aroma.

Blowoff tube

A hose from fermenter to a container of sanitizer to handle vigorous fermentation and prevent airlock clogs.

Bottle conditioning

Carbonating beer in the bottle by adding priming sugar and allowing yeast to ferment it.

Break (hot break, cold break)

Protein and polyphenol clumps that form during the boil (hot break) and during chilling (cold break). Helps clarify wort and beer.

Brettanomyces (Brett)

A yeast genus used in some farmhouse and sour styles. Can produce funky, fruity, earthy flavors and can ferment complex sugars.

C

Calcium (Ca)

A key brewing water ion that supports mash enzyme performance, helps yeast flocculation, and can improve clarity.

Carbonation

Dissolved CO2 in beer, creating bubbles and mouthfeel. Achieved via priming sugar, forced CO2, or spunding.

Carboy

A glass or plastic vessel often used for fermentation or aging.

Chloramine

A disinfectant used in some municipal water supplies. Can cause chlorophenols (band-aid flavors) unless removed (often with Campden tablets).

Chlorophenol

Medicinal, band-aid-like off-flavor often caused by chlorine or chloramine reacting with phenols from malt or yeast.

Clarifying agent (fining)

Ingredients used to help particles settle out – like Irish moss, Whirlfloc, gelatin, isinglass, or Biofine.

Cold crash

Chilling beer near freezing for 1-3 days to encourage yeast and haze particles to drop out.

Conditioning

Time after fermentation for beer to mature, clarify, and for flavors to round out.

Contamination

Unwanted microbes entering wort or beer. Can cause sourness, funk, phenols, diacetyl, or over-carbonation.

Conversion

The mash process of turning starches into sugars. Often checked with an iodine test or by time and temperature control.

Corn sugar (dextrose)

A common priming sugar and fermentable that is highly fermentable and relatively neutral in flavor.

CO2 line

The gas tubing that delivers CO2 from the regulator to a keg.

D

DA (Diastatic power)

A measure of a malt’s enzyme strength, indicating its ability to convert starches in the mash.

Decoction mash

A traditional method where part of the mash is boiled and returned to raise temperature and develop malt complexity.

Dechlorination

Removing chlorine or chloramine from brewing water, commonly with Campden (metabisulfite) or activated carbon filtration.

Diacetyl

A buttery or butterscotch flavor compound. Often reduced by healthy yeast and warm conditioning (diacetyl rest).

Diacetyl rest

Raising fermentation temperature near the end (especially for lagers) to help yeast clean up diacetyl and related compounds.

Dimethyl sulfide (DMS)

Cooked corn or cabbage-like aroma. Controlled by vigorous boiling and quick chilling, especially with lightly kilned malts.

Dissolved oxygen (DO)

Oxygen in finished beer that can lead to staling (paper, cardboard, muted hops). Minimize splashing after fermentation.

Dry hop

Adding hops after fermentation (or near the end) to boost aroma without much bitterness.

Dual-stage regulator

A CO2 regulator that reduces pressure in two steps for steadier output, helpful for consistent carbonation.

E

Efficiency (brewhouse efficiency)

How much potential sugar you extract from grain into the fermenter, compared to theoretical maximum.

Enzyme

Proteins that speed chemical reactions. In brewing, mash enzymes convert starches into sugars.

Esters

Yeast-produced fruity flavors and aromas (banana, pear, apple). Influenced by yeast strain, temperature, and fermentation health.

Evaporation rate

How much wort volume you lose during the boil per hour. Impacts pre-boil volume planning.

Extract (LME, DME)

Malt extract used in extract brewing – liquid malt extract (LME) and dry malt extract (DME).

F

False bottom

A perforated screen in a mash tun that supports the grain bed and helps separate wort from grain.

Fermentable

A sugar source yeast can consume (malt sugars, dextrose, sucrose, etc.).

Fermentation

The process where yeast convert sugars into alcohol, CO2, and flavor compounds.

Final gravity (FG)

Specific gravity after fermentation is complete. Used with OG to estimate ABV and dryness.

Fining

See clarifying agent – used to reduce haze and improve clarity.

Flocculation

How readily yeast clump together and settle out. Higher flocculation can mean clearer beer but sometimes less attenuation.

Forced carbonation

Carbonating beer in a keg by applying CO2 pressure, rather than using priming sugar.

Fusels (fusel alcohols)

Higher alcohols that can taste hot, solvent-like, or harsh. Often caused by high fermentation temperatures or stressed yeast.

G

Gelatin

A common cold-side fining that helps drop yeast and haze. Typically used after fermentation and often with cold crashing.

Glycol chiller

A cooling system that circulates chilled glycol through coils or jackets for tight fermentation temperature control.

Grain bill

The list and amounts of grains used in a recipe.

Gravity (specific gravity)

A measure of dissolved sugars in wort or beer. Expressed as OG and FG using a hydrometer or refractometer.

Grist

The milled grain used for mashing.

Growler

A container for transporting draft beer. Not ideal for long storage unless it is a pressurized growler.

Gypsum (calcium sulfate)

A brewing salt used to increase calcium and sulfate, often used to sharpen hop bitterness and dryness in hop-forward beers.

H

Hardness

Mineral content in water, often related to calcium and magnesium. Affects mash and flavor balance.

Haze (chill haze, permanent haze)

Cloudiness in beer. Chill haze appears cold and can fade warm; permanent haze may come from proteins, polyphenols, yeast, or starch.

Head retention

How well foam persists. Influenced by proteins, carbonation, serving method, and cleanliness of glassware.

Heat exchanger (wort chiller)

Equipment to cool wort quickly, commonly immersion, plate, or counterflow chillers.

Hop creep

Enzymes from dry hops can break down dextrins into fermentable sugars, causing renewed fermentation and potentially over-carbonation.

Hop stand (whirlpool addition)

Adding hops after flameout while wort is hot but not boiling, typically 160-190 F, to boost aroma and flavor.

Hot-side aeration (HSA)

Oxygen pickup while wort is hot, which may contribute to staling. Homebrew impact varies, but avoiding violent splashing is a good habit.

Hydrometer

A float tool used to measure specific gravity.

I

IBU (International Bitterness Units)

A rough measure of bitterness from isomerized hop compounds. Perceived bitterness also depends on malt balance, yeast, and water profile.

Iodine test

A test to check starch conversion in the mash. Iodine turns dark in the presence of starch.

Immersion chiller

A coil chiller placed in hot wort; cold water runs through the coil to cool the wort.

Infection

Brewing slang for microbial contamination, often detected by sourness, pellicle formation, or unexpected flavors.

Isomerization

The process where hop alpha acids convert into bitter iso-alpha acids during boiling.

J

Jump start (starter)

Informal way to describe using a yeast starter to increase cell count and improve fermentation performance.

Krausen ring (sometimes seen as a brown line)

Residue left on the fermenter wall from the foamy krausen during active fermentation.

K

Kegging

Packaging beer into a keg for serving and carbonation with CO2.

Kettle

The brewing pot used for boiling wort.

Kettle finings

Clarifiers added near the end of the boil (like Irish moss or Whirlfloc) to help coagulate proteins.

Kettle souring

Souring wort in the kettle using lactobacillus before boiling, commonly for quick sour beers.

Kolsch

A light, crisp ale fermented with a special yeast and conditioned cold, producing lager-like cleanliness.

Krausen

The foamy cap formed during active fermentation, made of yeast, proteins, and hop material.

L

Lactic acid

An acid used for mash pH adjustment or produced by lactic acid bacteria in sour beers.

Lager

Beer fermented with lager yeast (typically colder) and conditioned cold for a clean profile.

Lauter

Separating sweet wort from the grain bed after mashing.

LHBS (Local Homebrew Shop)

A local retailer specializing in brewing ingredients and equipment.

Line balancing

Matching beer line length and serving pressure to reduce foaming and pour consistently.

Liquor

Brewing term for water used in mashing and sparging (not spirits).

Lovibond (L)

A measure of malt color. Higher numbers indicate darker malts.

M

Malt

Grain (usually barley) that has been germinated and kilned to develop enzymes and flavor.

Maltster

A producer of malted grains.

Mash

Mixing milled grain with hot water to convert starch into sugars.

Mash pH

The acidity of the mash, typically targeted around 5.2-5.6 (measured at mash temperature adjusted reading). Impacts conversion and flavor.

Mash out

Raising mash temperature (often to about 168 F) to reduce viscosity and stop enzymatic activity before lautering.

Mead

A fermented beverage made from honey. Not beer, but often made by homebrewers.

Metabisulfite (Campden)

Tablets or powder used to remove chlorine or chloramine from water, and used for stabilization in some fermentations.

Micro-oxidation

Tiny oxygen exposure over time, sometimes used intentionally in barrel aging, but usually something to minimize in standard packaging.

Munich malt

A kilned base malt that adds bread crust and rich malt character.

N

Na (Sodium)

A brewing water ion. Small amounts can enhance fullness; too much can taste salty or harsh.

Noble hops

Traditional European hop varieties known for subtle, spicy, floral character (often used in lagers).

Nutrient (yeast nutrient)

Supplements that support healthy fermentation, especially in high gravity or low nutrient worts.

O

OG (Original gravity)

Specific gravity before fermentation starts. Indicates sugar content and potential alcohol.

Off-flavor

Any unwanted flavor or aroma, often from fermentation stress, oxidation, contamination, or process issues.

Oxygenation

Adding oxygen to cooled wort, often with pure oxygen and a diffusion stone, for strong or lager fermentations.

Oxidation

Staling reactions often caused by oxygen exposure after fermentation, leading to muted hops and papery,
sherry-like, or cardboard notes.

P

pH

A scale measuring acidity or alkalinity. Mash pH is one of the biggest levers for conversion, clarity, and flavor.

Pellicle

A film on the surface of beer formed by some wild yeasts or bacteria. Common in mixed fermentation, sometimes indicates infection in clean beers.

Pitch (yeast pitch)

Adding yeast to wort. Pitch rate, yeast health, and temperature matter.

Plate chiller

A compact heat exchanger that chills wort quickly by running wort and cold water through thin internal plates.

PPG (Points per pound per gallon)

A measure of extract potential. Used to estimate gravity contribution from grains or extract.

Priming sugar

Sugar added at packaging to create carbonation via bottle or keg conditioning.

Protein rest

A mash rest (often around 113-131 F) aimed at breaking down proteins. Useful for certain malts and high adjunct mashes, but not always needed.

PSI

Pounds per square inch, a pressure unit used on CO2 regulators.

Q

Quick disconnect (QD)

A fitting that allows fast connection and removal of gas or liquid lines from kegs.

Quinine

Not a brewing ingredient for beer, but sometimes referenced when comparing bitterness perceptions (tonic water bitterness) to hop bitterness.

R

Racking

Transferring beer from one vessel to another, often off sediment. Also used for packaging into kegs or bottles.

Refractometer

An optical tool to measure sugar concentration. Requires correction when alcohol is present.

Residual sweetness

Perceived sweetness from unfermented sugars and malt character, balanced by bitterness and acidity.

Rest (mash rest)

Holding the mash at a given temperature to achieve a specific enzymatic goal, like beta rest for fermentability.

Reverse osmosis (RO) water

Very low-mineral water made by filtration. Great for building a water profile from scratch using brewing salts.

RIMS

Recirculating infusion mash system – a method that recirculates wort through a heater to maintain mash temperature.

S

Sanitizer

Chemicals used to reduce microbes on equipment that touches cooled wort or beer (Star San and iodophor are common).

Saccharification

The mash process where enzymes convert starch to fermentable sugars.

Saccharification rest

The main mash rest, often around 146-158 F, where starch conversion happens.

Sediment

Yeast and particles that settle to the bottom of fermenters or bottles.

SG (Specific gravity)

The density of wort or beer compared to water. Used to estimate sugar content and fermentation progress.

Single infusion mash

A mash with one main temperature rest, common in modern homebrewing.

Sparge

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

Spunding

Capturing CO2 during fermentation under pressure to naturally carbonate beer in a sealed vessel.

Starter (yeast starter)

A small, oxygenated batch of wort used to grow yeast before pitching, improving cell count and vitality.

Stuck fermentation

When fermentation slows or stops before reaching expected FG. Causes can include low yeast health, temperature, low nutrients, or high gravity stress.

Stuck sparge

When wort flow through the grain bed stops or slows significantly, often due to a compacted bed or high beta-glucan grains.

Sulfate (SO4)

A water ion that can accentuate hop crispness and dryness. Often increased using gypsum.

Suspended trub

Fine particles in wort or beer that have not settled out, contributing to haze and sediment.

T

Tannins

Polyphenols from grain husks and hops that can cause astringency. Often extracted by overly hot sparging or high pH.

Thermowell

A tube in a fermenter that houses a temperature probe, allowing accurate readings inside the beer.

Tincture

A flavor extract made by soaking ingredients (vanilla, fruit peel, spices) in alcohol, then dosing into beer.

Trub

Protein, hop material, and break material left behind after boiling and chilling.

Two-stage fermentation

Sometimes used to describe primary fermentation followed by transfer for conditioning or aging, though many beers do fine in one vessel.

U

Underpitch

Pitching too little yeast. Can increase esters and stress flavors, and risk stalled fermentation.

Uptake (yeast uptake)

When yeast absorb nutrients and compounds from wort, including oxygen early and sugars throughout fermentation.

V

Varietal (hop varietal)

A specific hop variety (like Citra, Mosaic, Saaz) with a distinct aroma profile.

Vorlauf

Recirculating the first runnings from the mash until the wort runs clearer, then collecting into the kettle.

W

Water profile

The mineral composition of brewing water (calcium, magnesium, sodium, sulfate, chloride, bicarbonate) that influences mash chemistry and flavor perception.

Wheat beer

A beer style family using a significant portion of wheat, often with a soft, bready character and sometimes yeast-driven notes.

Whirlpool

Circulating wort after the boil to gather trub into a cone and to steep whirlpool hops for aroma.

Whirlfloc

A tablet fining used near the end of the boil to improve clarity.

Wild yeast

Non-cultured yeast present in the environment. Can be used intentionally in some styles, but is a contamination risk for clean beers.

Wort

Unfermented beer – the sweet liquid extracted from the mash, boiled with hops, then fermented.

X

Xylose

A sugar found in some plant materials. Most standard brewing yeast do not ferment xylose efficiently.

Y

Yeast

Microorganisms that ferment sugars into alcohol and CO2. Yeast strain choice heavily influences beer flavor.

Yeast cake

The layer of yeast and sediment at the bottom of a fermenter after fermentation.

Yeast nutrient

See nutrient – supports fermentation performance, especially in high gravity or lower nutrient worts.

Yeast washing

A debated homebrew practice referring to rinsing harvested yeast to separate it from trub. Many brewers instead harvest a clean portion and store cold.

Z

Zymurgy

The study of fermentation in brewing, winemaking, and distilling.

Zymase

A group of enzymes in yeast that help convert sugars into alcohol and CO2.