A colloquial phrase used to correct someone or say 'that's not it' / 'no, not like that'—used when indicating the right idea or correcting a misunderstanding.
A: 彼は医者なの？ B: そうじゃなくて、看護師だよ。
A: Is he a doctor? B: No, not like that — he's a nurse.
いや、そうじゃなくて、私が言いたかったのはもっと簡単なことです。
No, that's not it — what I meant was something much simpler.
友達に『疲れてるの？』と聞かれたとき、僕は『そうじゃなくて、ただ集中していただけ』と答えた。
When a friend asked me 'Are you tired?', I answered, 'No, not like that; I was just focused.'
そうじゃなくて、もっと具体的に説明してもらえますか？
No — could you explain it more concretely?