You'll notice that I use the word "ain't" once in a while. Personally I think it's a fine word -- or at least a fun word -- so I decided it was time to do a bit of research. It turns out that ain't is an alternate (and more common) spelling of "an't", which is a contraction for "am not" (some dialects of English contain "amn't" but that's hard to say, which is why the "m" was dropped). Now, an't or ain't came into broad use about the same time as most of our other verbal contractions -- aren't, isn't, can't, don't, and the like. So why did ain't come to have such a nasty reputation, whereas even grammatical prescriptivists are perfectly happy with isn't and aren't? Well, Dr. Language himself has investigated the matter and his conclusion is that ain't fills a gaping void in the English language, namely as a contraction for "am not" -- but that its use is warranted only with the first-person singular. Thus "ain't English grand?" does not cut the mustard, whereas "I ain't interested in your grammatical prescriptivism!" is just fine. Try it on for size!