買わなくて

not buy and...

→ 買う
買わ buy + なく Negative (adverbial form) + Te-form (conjunctive)
verb · necessitative Rare #26,774
not buy and... Used to connect a negative clause to what follows, often meaning “without buying” or “because one did not buy.”
JA: その本を買わなくてよかった。
EN: I'm glad I didn't buy that book.
Conjugation of 買う

その本は買わなくてよかったのに

You didn't have to buy that book.

水をマレーシアから買わなくてはならないのです

We have to buy water from Malaysia.

外国から買わなくてはなりません

We have to buy it from abroad.

こんなものを買わなくてよかった

I'm glad I didn't buy something like this.

そんな高い買わなくてよかったのに

You didn't have to buy such an expensive book.