請問ain't的全寫&意思是什麼?

'Ain't' appears in lots of songs, even when we are talking....
'Ain't' means a lot :
1. am not
2. do not
3. will not
4 are not
.
.
.
.

and any kind of these tenses...we only use this word when we're talking and singing songs, but don't use it in school's writing....

ain't=am not

解釋:不是<---咁解
長寫呢...唔知