An alcoholic beverage is a drink containing ethanol, commonly known as alcohol, although in chemistry the definition of alcohol includes many other compounds. Alcoholic beverages are divided into three general classes: beers, wines, and spirits.

Ethanol is a psychoactive drug that has a depressant effect. Most countries restrict and regulate its sale and consumption; for example, they place legal drinking-age restrictions upon the sale of alcoholic drinks to young people. The manufacture and consumption of alcohol occurs in most cultures and societies of the world, from hunter-gatherer peoples to nation-states. The drinking of alcoholic beverages is very often an important part of social events in such societies, and it can be an important aspect of a community's culture.

Ethanol is only slightly toxic compared to other alcohols, but has significant psychoactive effects. A significant blood alcohol content may be considered legal drunkenness as it reduces attention and slows reaction speed. Alcoholic beverages can be addictive and the state of addiction to ethanol is known as alcoholism.

Chemistry and toxicology

Ethanol (CH₃CH₂OH), the active ingredient in alcoholic drinks, for consumption purposes is always produced by fermentation – the metabolism of carbohydrates - by certain species of yeast in the absence of oxygen. The process of culturing yeast under alcohol-producing conditions is referred to as brewing. The same process produces carbon dioxide in situ, and may be used to carbonate the drink. However, this method leaves yeast residues and on the industrial scale, carbonation is usually done separately.

Drinks with a concentration of more than 50% ethanol by volume (100 US proof) are flammable liquids and easily ignited. Some exotic drinks gain their distinctive flavors through intentional ignition, such as the Flaming Dr Pepper. Spirits with a higher ethanol content can be ignited with ease by heating slightly, e.g. adding the spirit to a warmed shot glass.

In chemistry, alcohol is a general term for any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom, which in turn may be bound to other carbon atoms and further hydrogens. Other alcohols such as propylene glycol and the sugar alcohols may appear in food or beverages regularly, but these alcohols do not make them "alcoholic". Methanol (one carbon), the propanols (three carbons giving two isomers), and the butanols (four carbons, four isomers) are all commonly found alcohols, and none of these three should ever be consumed in any form. Alcohols are toxicated into the corresponding aldehydes and then into the corresponding carboxylic acids. These metabolic products cause a poisoning and acidosis. In the case of other alcohols than ethanol, the aldehydes and carboxylic acids are poisonous and the acidosis can be lethal. In contrast, fatalities from ethanol are mainly found in extreme doses and related to induction of unconsciousness or chronic addiction (alcoholism).