Google finds 52,000,000 matches for ain't but non-natives simply can't look up this word. Wiktionary isn't helpful. Is it some kind of 'wildcard' for "am/is/are not"?
Over 10 years ago saying "ain't" was discouraged but it was gaining momentum. What happened? Seems like it's still discouraged. Maybe in another 10 years?
When we have a button in a website for creating an account for a website. Should it say 'sign up' or 'signup'? I've seen 'sign up' on most of the places, but which is the correct one?