'ain't' is a contraction of any of the following: am not, is not, are not, have not, or has not "I ain't able of that" is wrong., because you can't say ' able of ' ,you either say 'able to' or 'capable of' and both have the same meaning then. " I ain't capable of that."or " I ain't able to do that." ( In both cases 'ain't ' is a contraction of ' am not' Other examples of how to use 'ain't;" - He ain't ready for it ( contraction for 'is not') - They ain't got any money yet ( contraction for 'have not') P.S : 'ain't' is a nonstandard word!

I agree with the above- don't use it!! It sounds very uneducated.