any of a variety of alcoholic beverages produced by the fermentation of starchy material derived from grains or other plant sources.

Known to the Egyptians, Babylonians, and probably to earlier civilizations, beer became the common beverage in northern climates not conducive to grape cultivation. Although beer and wine are both fermented and undistilled, wine is made from basic materials rich in natural sugar, while beer is made from materials high in starch content. Starches must be converted to sugar before fermentation can occur.

Most of the world's beers are made from malted barley and flavoured with hops. They may be produced by employing a bottom-fermenting yeast strain, which falls to the bottom of the container when fermentation is completed, or a top-fermenting strain, which releases carbon dioxide and rises to the surface, forming a head.

Lager beers, preferred in the United States, are aged beers of German origin, taking their name from the German lagern ("to store"). Bottom-fermented, they are stored at a low temperature for several months, clearing, acquiring mellowness, and becoming charged with carbon dioxide. Most lagers are light in colour, with high carbonation, medium hop flavour, and alcohol content of 3-5 percent by volume. They include Pilsener, Dortmund, Munich, and California steam beer. Top-fermented beers, popular in Great Britain, include ale, stout, and a brew intermediate between the two, called porter. They have a sharper, more strongly hopped flavour than lagers and alcohol content ranging from 4 to 6.5 percent or more by volume.

Beers made from raw materials other than barley include hundreds of local African drinks made from millet, sorghum, and other available starch crops; Russian kvass, made from fermented rye bread; Chinese samshu, Korean suk, and Japanese sake, all brewed from rice; and pulque, an indigenous Mexican beer made from the fermented sap of the agave plant. The Mexicans and the Japanese also brew and export several brands of Western-style beer.