않았을까

In a sentence

• 그가 오지 않았을까 생각했다.

  I wondered if he hadn't come.

  In this sentence, '않았을까' is used to express a reflective or speculative mood about the possibility of an action's negative occurrence.

• 비가 오지 않았을까 걱정했어요.

  I was worried that it might not have rained.

  Here, '않았을까' indicates concern about an unlikely scenario regarding a past event.

• 시험이 너무 어렵지 않았을까 놀랐다.

  I was surprised that the test might not have been too difficult.

  In this case, '않았을까' raises a speculative thought about the inverse degree of difficulty of the test.