Beer glossary: essential terms from ABV to wort

Terms A to Z

Abbey beer

Beer brewed in a monastic style, often under licence from a real or historical abbey, by a commercial brewery. Leffe and Grimbergen are abbey beers; they are not Trappist beers.

ABV

Alcohol by volume: the percentage of a beer's volume that is ethanol. Most lagers sit between 4 and 5.5% ABV; imperial stouts and quadrupels often reach 9 to 13%.

ABW

Alcohol by weight: alcohol content measured as a share of mass rather than volume. Because ethanol is lighter than water, ABW is about 80% of the ABV figure. Rarely used on labels today.

Adjunct

Any fermentable ingredient other than malted barley, such as rice, corn, unmalted wheat, oats or sugar. Adjuncts lighten body and flavor in many mass-market pale lagers.

Alpha acids

Resin compounds in hop cones, chiefly humulone, that become bitter iso-alpha acids when boiled. A hop's alpha acid percentage tells brewers how much bitterness it will contribute.

Attenuation

The share of sugars in the wort that yeast converts into alcohol and carbon dioxide. High attenuation gives a dry, thin beer; low attenuation leaves residual sweetness and body.

Barrel-aged

Beer matured in wooden barrels, often ones that previously held bourbon, wine or other spirits. The wood adds vanilla, oak and spirit character, and may host wild microbes.

Bottle conditioning

Refermentation inside the bottle after a small dose of sugar and yeast is added at packaging. It creates natural carbonation and leaves a yeast sediment, common in Belgian ales.

Brettanomyces

A genus of wild yeast, nicknamed Brett, that produces earthy, leathery, barnyard and tropical aromas. It is essential in lambic, Orval and many American wild ales, but a fault in most other beers.

Brewhouse

The part of a brewery where wort is made: the mash tun, lauter tun, kettle and whirlpool. Its capacity is usually expressed in hectoliters or barrels per brew.

Brut IPA

A very dry, highly carbonated IPA made by adding the enzyme amyloglucosidase to ferment almost all sugars. Created in San Francisco in 2017 by Kim Sturdavant of Social Kitchen.

Cask ale

Unfiltered, unpasteurized beer that finishes conditioning in the cask from which it is served, usually by hand pump. Championed in Britain by CAMRA as real ale.

Cold crashing

Rapidly chilling beer near 0 °C after fermentation so yeast and haze particles drop out. It clarifies beer before packaging without filtration.

Decoction

A mashing method in which part of the mash is removed, boiled and returned to raise the temperature. Traditional in Czech and German lager brewing, it deepens malt flavor.

Diacetyl

A compound produced during fermentation that tastes of butter or butterscotch. It is a fault in most lagers, tolerated at low levels in some English ales and Czech lagers.

DMS

Dimethyl sulfide, a compound with an aroma of cooked corn or cabbage. It forms from pale malt and is driven off by a vigorous, uncovered boil.

Double IPA

A stronger, more bitter and more heavily hopped IPA, usually 7.5 to 10% ABV. Also called imperial IPA. Popularized in California in the 1990s.

Dry hopping

Adding hops to beer during or after fermentation rather than during the boil. It adds aroma without much bitterness and is central to modern IPAs.

EBC

European Brewery Convention color scale. A pilsner measures about 4 to 10 EBC and a stout above 60. EBC is roughly 1.97 times the SRM value.

Esters

Fruity aroma compounds produced by yeast, such as isoamyl acetate, which smells of banana. Warm fermentation increases ester levels, which is why ales are fruitier than lagers.

Final gravity

The density of beer after fermentation, measured against water. Compared with original gravity, it shows how much sugar was fermented and allows ABV to be calculated.

Firkin

A British cask holding 9 imperial gallons, about 40.9 liters. It is the most common cask size for real ale in pubs.

Gose

A tart wheat beer brewed with coriander and salt, originally from Goslar and later Leipzig in Germany. It is now popular with craft brewers, often with fruit.

Grist

Milled malt and other grains ready to be mixed with hot water in the mash. The grist bill is the brewer's list of grains and their proportions.

Growler

A refillable glass or steel jug, typically 1.9 liters (64 US fl oz), used to carry draft beer home from a brewery or bar.

Gruit

A mixture of herbs such as bog myrtle, yarrow and rosemary used to flavor and preserve beer in medieval Europe before hops became standard.

Gueuze

A blend of young and old lambics, typically one, two and three years old, bottled to referment into a dry, sparkling and sour beer. Brewed around Brussels.

Hazy IPA

Also called New England IPA: an IPA with low bitterness, a soft body and a cloudy appearance, heavily dry hopped for juicy tropical aromas. Emerged in Vermont in the 2000s.

Head retention

How long the foam on a poured beer lasts. Proteins from malt, especially wheat, and hop compounds improve it; grease and detergent residue in glasses destroy it.

Hectoliter

One hundred liters, the standard unit for beer production volumes outside the United States. World output was about 1.875 billion hectoliters in 2024.

Hop

The cone-shaped flower of Humulus lupulus, used in beer for bitterness, aroma and preservation. Major growing regions include Hallertau in Germany and the Yakima Valley in the US.

Hop burst

A technique where most hops are added late in the boil or in the whirlpool, maximizing flavor and aroma while keeping harsh bitterness lower.

IBU

International Bitterness Units: milligrams of iso-alpha acids per liter of beer. Mass-market lagers measure 8 to 15 IBU; West Coast IPAs often exceed 60.

Imperial

A prefix meaning a stronger, more intense version of a style, such as imperial stout or imperial IPA. It comes from strong stouts exported to the Russian imperial court.

Isinglass

A fining agent made from fish swim bladders, added to cask ale to clear yeast quickly. Its use means many cask beers are not vegan.

Keg

A pressurized metal container for draft beer, usually 20, 30 or 50 liters in Europe. Unlike cask ale, keg beer is typically filtered and served with added gas pressure.

Kettle souring

A fast souring method in which wort is inoculated with Lactobacillus before the boil, then boiled to kill the bacteria. Used for quick Berliner weisse and gose.

Krausen

The thick, rocky foam of yeast and proteins that forms on top of fermenting beer. Krausening also means adding actively fermenting wort to finished beer to carbonate it.

Lactobacillus

Lactic acid bacteria that sour beer by converting sugars into lactic acid. Used in Berliner weisse, gose and many modern sour ales.

Lagering

Cold storage of beer, usually near 0 °C for weeks after fermentation. From the German lagern, to store. It clarifies the beer and smooths its flavor.

Lambic

A Belgian wheat beer spontaneously fermented by wild yeast and bacteria from the air of the Senne valley around Brussels. It is aged in wooden barrels, often for years.

Lauter tun

A vessel with a slotted false bottom used to separate wort from spent grain after mashing. The grain husks form a natural filter bed.

Light-struck

A skunky off-flavor caused when ultraviolet and blue light break down hop compounds. Clear and green bottles offer little protection; brown glass and cans block it.

Malt

Grain, usually barley, that has been steeped, germinated and dried in a kiln. Malting develops the enzymes and sugars brewers need, and kilning sets color and flavor.

Mash

The mixture of milled grain and hot water in which malt enzymes convert starch into sugars, typically held at 62 to 72 °C for about an hour.

Mouthfeel

The physical sensation of beer in the mouth, including body, carbonation, creaminess and astringency. Judges score it separately from aroma and flavor.

Nitro

Beer served with a nitrogen and carbon dioxide gas mix, producing small bubbles, a dense head and a creamy texture. Guinness Draught is the best-known example.

Noble hops

Four traditional European aroma hops: Hallertauer Mittelfrüh, Tettnanger, Spalter and Saaz. They are low in bitterness and known for spicy, floral notes.

Original gravity

The density of wort before fermentation, indicating how much sugar it contains. Expressed as specific gravity, such as 1.048, or in degrees Plato.

Oxidation

Staling caused by oxygen exposure, producing papery, cardboard or sherry-like flavors. Brewers limit oxygen during packaging to slow it.

Pasteurization

Heating beer to kill microorganisms and extend shelf life, named after Louis Pasteur. Done in the package (tunnel) or before filling (flash).

Pediococcus

Lactic acid bacteria that produce sourness and, given time, diacetyl. Found in lambic and Flanders red ales, where Brettanomyces later cleans up the diacetyl.

Phenols

Aroma compounds that can smell of clove, pepper or smoke. Desired in German wheat beers and saisons, a fault in most other styles.

Pitching

Adding yeast to cooled wort to start fermentation. The pitch rate, the number of yeast cells added, affects fermentation speed and flavor.

Plato

A scale expressing the sugar content of wort as a percentage by weight. Commonly used in Europe; 12 °P corresponds to a specific gravity of about 1.048.

Real ale

A term coined by CAMRA in the 1970s for beer conditioned and served from the cask or bottle without filtration, pasteurization or added carbon dioxide.

Session beer

A beer low enough in alcohol, usually under 5% ABV, to drink several in one sitting while keeping balance and flavor.

Sparging

Rinsing the grain bed with hot water after mashing to extract remaining sugars into the wort. Typically done at around 75 to 78 °C.

Spontaneous fermentation

Fermentation started by wild yeast and bacteria from the environment rather than a cultured yeast. Used for lambic, where wort cools overnight in an open vessel.

SRM

Standard Reference Method, the American beer color scale. A pale lager measures 2 to 4 SRM, an amber ale around 15, and a stout 30 or more.

Staling

The loss of fresh flavor as beer ages, mainly through oxidation. Hop aroma fades first, which is why IPAs are best drunk within a few months of packaging.

Top-fermenting

Describes ale yeast, Saccharomyces cerevisiae, which ferments warm and traditionally collects at the surface. Bottom-fermenting describes lager yeast, which settles at the base.

Trappist

A protected label for beer brewed inside a Trappist monastery under the monks' supervision, with profits for the community or charity. Certified by the International Trappist Association since 1997.

Trub

Sediment of proteins, hop matter and dead yeast that settles out of wort or beer after the boil and after fermentation. Brewers remove it to improve clarity.

Vorlauf

Recirculating the first cloudy runnings of wort back over the grain bed until they run clear, before collecting wort for the kettle.

Whirlpool

A step or vessel after the boil where wort is spun so solids collect in a central cone. Hops added here give aroma with limited bitterness.

Wild ale

Beer fermented wholly or partly with wild yeast or bacteria such as Brettanomyces, Lactobacillus or Pediococcus. Often sour and barrel-aged.

Wort

The sweet liquid drained from the mash, containing the sugars yeast will ferment. It is boiled with hops before fermentation. Pronounced wurt.

Yeast

Single-celled fungi that convert sugar into alcohol and carbon dioxide. Brewing uses mainly Saccharomyces cerevisiae for ales and Saccharomyces pastorianus for lagers.

Zwickel

The sampling valve on a lagering tank. Zwickelbier is unfiltered lager drawn young, similar to kellerbier, with a hazy look and fresh yeast character.

Frequently asked questions