ain't

 
Pronunciation: /eɪnt/
informal

contraction

  • am not; are not; is not: if it ain’t broke, don’t fix it
    [first representing London dialect]
  • has not; have not: they ain’t got nothing to say
    [from dialect hain't]

The use of ain’t was widespread in the 18th century, typically as a contraction for am not. It is still perfectly normal in many dialects and informal speech in both Britain and North America. Today, however, it does not form part of standard English and should never be used in formal or written contexts. See also are n’t (usage).