"Ain't" is an informal spoken form and is used as follows: I am not = I ain't You are not = You ain't He/She/It is not = He/She/It ain't We are not = We ain't They are not = They ain't It can also be used as a replacement for "have not": I have not = I ain't You have not = You ain't He/She/It has not = He/She/It ain't We have not = We ain't They have not = They ain't Please note, however, that "ain't" is a purely spoken form and should never be used in written English. Furthermore, the use of "ain't" by native-speakers of English tends to suggest a low level of education and poor control of language. In the UK is it a form mostly used by teenagers and the (usually) ill-educated lower/working classes. Except in extremely special cases for effect or emphasis, I NEVER use "ain't" and I would not recommend students to use it either.

Hi Anna 'ain't' is actually not a correct English word, its a word that was invented by people who can't speak English properly! It's typically used by uneducated people as well, don't use this word in English! It's on lots of American films but its not a real word! It is supposed to mean 'not' as in I'm not..... but its very bad English and shouldn't be used.