부르던

In a sentence

• 그녀가 부르던 노래는 매우 아름다웠다.

  The song she used to sing was very beautiful.

  Here, "부르던" modifies "노래" to indicate that it was a song sung in the past or habitually by her.

• 우리가 부르던 친구가 드디어 도착했다.

  The friend we were calling out to has finally arrived.

  Here, "부르던" refers to the continuous or repeated action of calling the friend earlier.

• 아이들이 부르던 동요가 모두를 미소짓게 했다.

  The kids' singing of nursery rhymes made everyone smile.

  Here, "부르던" describes the action of singing nursery rhymes by the children in a habitual or ongoing sense.