何

1. pronoun what
2. you-know-what; that thing
3. whatsit; whachamacallit; what's-his-name; what's-her-name
4. noun, colloquial, usually in kana, esp. ナニ penis; (one's) thing; dick
5. adverb, with neg. sentence (not) at all; (not) in the slightest
6. interjection, indicates surprise what?; huh?
7. indicates anger or irritability hey!; come on!
8. used to dismiss someone's worries, concerns, etc. oh, no (it's fine); why (it's nothing); oh (certainly not)

なん

1. pronoun what
2. prefix, followed by a counter how many
3. followed by (optional number), counter and も many; a lot of
4. followed by a counter and か several; a few; some