불가능하다

In a sentence

• 이 문제를 해결하는 것은 불가능하다.

  It is impossible to solve this problem.

  Here, '불가능하다' is used descriptively to indicate that the action of solving the problem cannot be accomplished.

• 그가 시간을 지키는 건 정말 불가능해 보여요.

  It really seems impossible for him to be punctual.

  In this sentence, '불가능하다' expresses the subjective impression that punctuality cannot be achieved by the subject.

• 모든 일은 불가능해 보였지만 우리는 끝내 성공했다.

  Everything seemed impossible, but we finally succeeded.

  Here, '불가능하다' is used in a past context to describe the appearance of infeasibility before an eventual success.