Beer is a lightly alcoholic and carbonated beverage made with water, fermented malt and plant components, such as herbs and hops, (or extracts thereof) that serve to flavor and/or preserve the beer. Beer is one of the oldest alcoholic beverages in the world and the most widely consumed of them, and the second most popular beverage after water and tea.

There are several ways to make beer. The most common method used in Europe and North America is to ferment (alcoholic fermentation) the malt of barley in water with a yeast of the genus Saccharomyces. Carbon dioxide and alcohol are formed during this process. Before fermentation, hop cones, the female flowers of hops, are boiled along as a flavoring and preservative.