Korean grammar patterns › Level 3
-는 사이(에)
while, in the (short) time that
Level 3 · TOPIK II · intermediate
How to use it
Clause 2 happens during the (often short) time of clause 1, typically something unexpected. -(으)ㄴ 사이에 when clause 1 is a completed action (나간 사이에 = while someone was out).
Forming it
| 자다 | → 자는 사이에 |
| 나가다 | → 나간 사이에 |
| 보다 | → 안 보는 사이에 |
Examples
제가 자는 사이에 동생이 제 과자를 다 먹었어요.
While I was sleeping, my younger brother ate all my snacks.
잠깐 안 보는 사이에 아이가 많이 컸네요.
The child has grown so much in the short time I didn't see him.
Compared with similar patterns
-는 동안 is neutral about a period of time (often longer); -는 사이에 suggests a brief time in which something unexpected happens.