I'm writing a story in which a character's birthday (May 1st) is significant. A characters notes in conversation that, "Her birthday is May first." Should I write out 'first' or refer to it as '1st'? ...
Is it just because "ninth" has only one syllable? That wouldn't make sense, though, because saying "NINE-ith" wouldn't be worse than saying "NINE-e-tee". If we were used to "nineth", we would have ...