ha

1. ha; aha
   Ha! Znao sam da si ti uzeo ključeve. — Ha! I knew you took the keys.
   Ha, evo ga, našao sam telefon! — Aha, here it is, I found the phone!
2. (usually repeated) ha
   Ha-ha, baš si smešan! — Ha-ha, you're so funny!
3. colloq. (at the end of a question) huh?; eh?
   Šta sad hoćeš, ha? — What do you want now, huh?
   Lepo si se provela, ha? — You had a good time, eh?

As a question tag, "ha?" is familiar and can sound rude.