Teetotalism (or T-total) is the practice an promotion of complete abstinence from alcoholic beverages. A person who practices (and possibly advocates) teetotalism is called a teetotaler or teetotaller (plural teetotalers or teetotallers). Such people are said to be on the wagon unless they've never consumed alcoholic beverages (someone who is 'on the wagon' has usually needed to stop drinking, hence 'falling off the wagon').