-(으)ㄴ/는/(으)ㄹ 줄 몰랐다[알았다]
'-줄 알았다' expresses a false assumption (thought X was true, but it wasn't). '-줄 몰랐다' expresses surprise at a fact one was previously unaware of.
Summary
Equivalent
I didn't know that... / I thought (wrongly) that...
Example
I didn't know that today was a public holiday.
오늘이 공휴일인 줄 몰랐어요.
Grammar rules
- Related to the beginner '-(으)ㄹ 줄 알다/모르다' (know HOW to do), but these tense-modified versions express a FACT or SITUATION, not a skill.
- 수미가 올 줄 몰랐어요 (I didn't know Sumi would come) vs 피아노를 칠 줄 몰라요 (I don't know how to play piano) — distinguish the two uses.
이렇게 어려울 줄 몰랐어요. (I didn't know it would be this difficult.)
Patterns
Verbs (Past Realization)
Past · Verb Stem + (으)ㄴ 줄 알았다/몰랐다
Verbs (Present Realization)
Present · Verb Stem + 는 줄 알았다/몰랐다
Verbs (Future Realization)
Future · Verb Stem + (으)ㄹ 줄 알았다/몰랐다
Adjectives (Present State Realization)
Present · Adjective Stem + (으)ㄴ 줄 알았다/몰랐다
Example sentences
I didn't know that today was a public holiday.
오늘이 공휴일인 줄 몰랐어요.
I thought it would rain so I brought an umbrella, but it's not raining.
비가 올 줄 알고 우산을 가져왔는데 안 오네요.
I thought that person was a foreigner.
그 사람이 외국인인 줄 알았어요.
Conversation
A: Oh, Andy. You haven't left work yet?
어, 앤디 씨. 아직 안 퇴근했어요?
B: Yes, I thought you had already left work.
네, 저는 앤디 씨가 벌써 퇴근한 줄 알았어요.
Practice
Fill in the blank
Select the correct tense-modified realization form.
Eating (Present Verb).
Expensive (Adj Present).