못한다

In a sentence

• 나는 수영을 못한다.

  I cannot swim.

  Here, '못한다' expresses inability to perform the action of swimming.

• 그는 시간 때문에 약속을 지키지 못한다.

  He cannot keep the appointment due to time constraints.

  In this context, '못한다' is used to explain the reason for failing to keep the appointment.

• 그녀는 너무 긴장해서 말도 못한다.

  She is so nervous that she cannot even speak.

  Here, '못한다' illustrates the impact of nervousness, resulting in the incapacity to speak.