Acetaldehyde: Green apple aroma, a byproduct of fermentation.

Additive: Enzymes, preservatives, and antioxidants which are added to simplify the brewing process or prolong shelf life.

Adjunct: Fermentable material used as a substitute for traditional grains, to make beer lighter-bodied or cheaper.

Alcohol: Ethyl alcohol or ethanol. An intoxicating by-product of fermentation, which is caused by yeast acting on sugars in the malt. Alcohol content is expressed as a percentage of volume or weight.

Alcohol by weight: Amount of alcohol in beer measured in terms of the percentage weight of alcohol per volume of beer.

Alcohol by volume: Amount of alcohol in beer in terms of percentage volume of alcohol per volume of beer.

All-malt: A relatively new term in America. "All malt" refers to a beer made exclusively with barley malt and without adjuncts.

Anaerobic: An organism, such as a bottom-fermenting lager yeast, that is able to metabolize without oxygen present.

Barley: A cereal grain that is malted for use in the grist that becomes the mash in the brewing of beer.

CAMRA: The CAMpaign for Real Ale. An organization in England that was founded in 1971 to preserve the production of cask-conditioned beers and ales.

Enzymes: Catalysts that are found naturally in the grain. When heated in mash, they convert the starches of the malted barley into maltose, a sugar used in solution and fermented to make beer.

Ester: Volatile flavor compound naturally created in fermentation. Often fruity, flowery, or spicy.

Estery: Aroma or flavor reminiscent of flowers or fruits.

Fermentation: Conversion of sugars into ethyl alcohol and carbon dioxide, through the action of yeast.

Gravity: See specific gravity.

Hefe: A German word meaning "yeast". Used mostly in conjunction with wheat (weiss) beers to denote that the beer is bottled or kegged with the yeast in suspension (hefe-weiss). These beers are cloudy, frothy and, very refreshing.

IBU: International Bitterness units. A system of indicating the hop bitterness in finished beer.

Lager: Beers produced with bottom fermenting yeast strains, Saccharomyces uvarum (or carlsbergensis) at colder fermentation temperatures than ales. This cooler environment inhibits the natural production of esters and other byproducts, creating a crisper tasting product.

Saccharomyces cerevisiae: See Top-fermenting yeast.

Saccharomyces uvarum: See Bottom-fermenting yeast.

Saccharomyces carlsbergensis: See Bottom-fermenting yeast.

Secondary fermentation: Stage of fermentation occurring in a closed container from several weeks to several months.

Specific gravity: A measure of the density of a liquid or solid compared to that of water ((1.000 at 39°F (4°C))).

Sparge: To spray grist with hot water in order to remove soluble sugars (maltose). This takes place at the end of the mash.

Wort: The solution of grain sugars strained from the mash tun. At this stage, regarded as "sweet wort", later as brewed wort, fermenting wort and finally beer.

Yeast: A micro-organism of the fungus family. Genus Saccharomyces.