N3
ではなくて・じゃなくて
Not A but B, Conjunctive
赤いのではなくて、青いのをください。
Please give me the blue one, not the red one.
Explanation
「AではなくてB」 means 'not A but B'. You first deny a wording that could be misunderstood, then state the real fact, reason or right way. In speech: 「じゃなくて」. Nouns attach directly; for a verb or a clause add 「の / ん」: 「行くのではなくて、帰るんです」 (I'm not going, I'm coming back).
Mixed up with
Style: 「~ではなくて」 is for standard writing or formal speech; 「~じゃなくて」 is casual speech; 「~ではなく」 (without 「て」) is for formal writing and papers, as a pause form.
To correct a reason or motive, use 「Aからではなくて、Bからだ」 (not because of A, but because of B). Exams often test how 「の」 and the connecting words fit together.