Alcoholic beverage made usually from malted barley, flavoured with hops, and brewed by slow fermentation. Known from ancient times, beer was especially common in northern climates not conducive to grape cultivation for wine. It is produced by employing either a bottom-fermenting yeast, which falls to the bottom of the container when fermentation is completed, or a top-fermenting yeast, which rises to the surface. Lager beers (from lagern, to store), of German origin, are bottom-fermented and stored at a low temperature for several months; most are light in colour, with high carbonation, medium hop flavor, and alcohol content of 3–5% by volume. Top-fermented beers, popular in Britain, include ale, stout, and porter; they are characterized by a prominent head of released carbon dioxide, a sharper and more strongly hopped flavour than lagers, and an alcohol content of 4–6.5% by volume. See alsomalt.