아니구나

In a sentence

• 그게 사실이 아니구나.

  That is not true.

  Here, '아니구나' serves as a realization or conclusion within a thought, expressing that something is determined not to be the case.

• 그 사람이 의사 아니구나.

  That person is not a doctor.

  In this sentence, '아니구나' is used to express a deduction or understanding that the person is concluded not to be a doctor.

• 여기가 역이 아니구나.

  This is not the station.

  Similarly, here '아니구나' indicates a realization or understanding that the place is concluded not to be the station.