I want to say to my friend "don't eat". What's the difference between these two:
1) tabenai de 食べないで
2) taberu na 食べるな
Taberuna (食べるな）is rather a masculine wording and tabenaide (食べないで）is rather a feminine wording.
The two are both impolite and rude in formal settings. In informal settings, for example, to your very close friends, you can use them.
edit) 食べるな may sound still rude. I advise you to use 食べないで or 食べないでね to your friends, even if you are a man.