This is really interesting! Thanks for the info. In English, hayatteru would be something like "to be in fashion", "to be fashionable", "to be in style", "to be stylish" or "to be popular". With words specifically, however, you would call it "slang". Tatoeba: Me: What does Daniel mean when he says "sup, bro"? Friend: Oh, it's slang. He means "how're you doing, friend?" I would've typed it in Japanese but the computer I'm using unfortunately doesn't have a Japanese option :S I can try to explain in Japanese later if you'd like :) Hope that helps