I asked this question way back on the old AOL board, but no one seemed to be able to give an answer, so I’ll try it here.
OK, you’ve got a word, possible, for example.
We’ll say it’s a new word and we don’t have its antonym yet. How do you decide what negative prefix to use? Is there a grammar rule for this situation? I know the word is IMpossible and it sounds good, but why couldn’t it have been UNpossible (I know, Ralph said on the Simpsons to be funny) or NONpossible?