Homo is not really a synonym for vir. Vir means a male human, homo simply means a human being.
The Vocative of "vir" is never "vire". Its only "sometimes" spelled as "vire" when beginning Latin students get it wrong. Vir counts as a 2nd Declension -er noun. Only the 2nd Declension -us nouns have Vocative Singular ending in -e.
I just wanted to make the very same point – the voc. of uir is never uire.—Schmidhauser (talk) 12:40, 19 January 2013 (UTC)