n.
Alcoholic beverage made usually from malted barley , flavoured with hop s, 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 35% 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 46.5% by volume. See also malt .