Beer is one of the oldest and most widely consumed alcoholic drinks in the world, and the third most popular drink overall after water and tea. Beer is brewed from cereal grains—most commonly from malted barley, though wheat, maize (corn), and rice are also used. During the brewing process, fermentation of the starch sugars in the wort produces ethanol and carbonation in the resulting beer. Most modern beer is brewed with hops, which add bitterness and other flavours and act as a natural preservative and stabilizing agent. Other flavouring agents such as gruit, herbs, or fruits may be included or used instead of hops. In commercial brewing, the natural carbonation effect is often removed during processing and replaced with forced carbonation.
Some of humanity's earliest known writings refer to the production and distribution of beer: the Code of Hammurabi included laws regulating beer and beer parlours, and "The Hymn to Ninkasi", a prayer to the Mesopotamian goddess of beer, served as both a prayer and as a method of remembering the recipe for beer in a culture with few literate people.
Beer is distributed in bottles and cans and is also commonly available on draught, particularly in pubs and bars. The brewing industry is a global business, consisting of several dominant multinational companies and many thousands of smaller producers ranging from brewpubs to regional breweries. The strength of modern beer is usually around 4% to 6% alcohol by volume (ABV), although it may vary between 0.5% and 20%, with some breweries creating examples of 40% ABV and above. Beer forms part of the culture of many nations and is associated with social traditions such as beer festivals, as well as a rich pub culture involving activities like pub crawling and pub games such as bar billiards.
Various legal definitions of beer exist in different countries. Historically, the most famous of these was the Reinheitsgebot, which applied to parts of the Holy Roman Empire and Germany and required beer to be made from only water, hops, and barley. Today in Canada, the Canadian Government's Food and Drug Regulations state that beer must have alcohol content that ranges from 1.1% to 8.6%, though it also includes a stipulation that it could be greater than 8.6% and labeled accordingly. Beer in South Korea must have less than 25% ABV, which means that it has to be 25 mL of alcohol or less per 100 mL of solution, and can be considered ‘lite’ only if it has less than 30 kcal per 100ml. Additionally, beer in South Korea must use only water, hops, and starches (wheat, rice, barley, corn, or potato) as ingredients in the brewing process. In Singapore, beer must have at minimum 1.0% alcohol by volume concentration at 20 °C. It is often brewed from a mixture of grains like malt, sugars or its equivalent, and hops or other vegetables