* The correct spelling is 멋있잖아.
* verb stem + 잖아 : 잖아 is used to confirm the fact or correct the error to the listener. 잖아 is mostly used in speech not in written language.
e.g. 내 방에 들어오지 말라고 했잖아. (I told you not to come into my room.)
e.g. A : 오늘 왜 이렇게 길이 막히지? (Why is the traffic so heavy today?)
B : 오늘 비가 오잖아. (Because it's rainy today.)
e.g. A : BTS를 왜 좋아해? (Why do you like BTS?)
B : 멋있잖아! (Because they are awesome!)
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