Beer is the world's most widely consumed[1] and likely the oldest[2][3][4] alcoholic beverage; it is the third most popular drink overall, after water and tea.[5] The production of beer is called brewing, which involves the fermentation of starches, mainly derived from cereal grains—most commonly malted barley, although wheat, maize (corn), and rice are widely used.[6] Most beer is flavoured with hops, which add bitterness and act as a natural preservative, though other flavourings such as herbs or fruit may occasionally be included