Ain’t is a contraction for am not, is not, are not, has not, and have not in the common English language vernacular. In some dialects ain’t is also used as a contraction of do not, does not, and did not. The development of ain’t for the various forms of to be not, to have not, and to do not occurred independently, at different times. The usage of ain’t for the forms of to be not was established by the mid-18th century, and for the forms of to have not by the early 19th century.
The usage of ain’t is a continuing subject of controversy in English. Ain’t is commonly used by many speakers in oral and informal settings, especially in certain regions and dialects. Its usage is often highly stigmatized, and it can be used by the general public as a marker of low socio-economic or regional status or education level. Its use is generally considered non-standard by dictionaries and style guides except when used for rhetorical effect.