掲示板 Forums - 「~じゃん」

It's kinda like saying だめです, but in a very soft, casual way. A bit like saying "that's no good" or "that won't do". In the dictionary it's this じゃん​

It's a bit hard to translate.

Edit: The exact meaning of だめじゃん also depends on context, tone and delivery. If aimed at someone, it can mean "Come on..." or even "You suck..."

Not in like a mean way though. It's usually playful, not harsh.

You're welcome! I guess I should also mention that じゃん is the casual contraction of じゃない, and is often used as a tag question (isn't it?). Usually more of a rhetorical question. For example: 楽しいじゃん → "this is fun, isn't it".

The ～じゃん in だめじゃん！ originates from the ～じゃない tag-question grammar, but in everyday use it's practically a statement (not really a rhetorical question).

Anyway, I thought I'd elaborate a bit, since I didn't really explain じゃん.