Ain't

The contraction ain't is a contraction for am not. Despite the fact that it has been in widespread use since the 18th century and is still normal in many dialects and informal speech, it is not considered standard English, and should not be used in formal or written contexts.

Be (not)
It is commonly used for am not; are not and is not, etc., as in I ain't so sure.; Ain't they ready?

Have (not)
It's also used as a contraction for has not and have not: I ain't been there for a long time; He ain't got a job.

Aren't
As "ain't" isn't acceptable, it is often replaced in speech with "aren't" as in I'm right, aren't I?, though there are also objections to this. The more formal version of this is I am right, am I not?. Some people, for example speakers of Scottish and Irish English, use the contraction "amn't I?".