-ㄴ/는/ㄹ 줄 몰랐다
I Didn’t Know That…, I Had No Idea That…
Used to say 'I didn't know that...' or 'I had no idea that...' when you learn something new and surprising. It implies you had a different assumption before.
How It Works
This expression is used to convey that the speaker has just learned something new that contradicts their previous assumptions or lack of knowledge. The key is the element of surprise or realization.
Conjugation Rules:
The form depends on the tense and word type.
1. Adjectives & 이다/아니다 (Present State):
Use -ㄴ/은 줄 몰랐다.
- Vowel stem + -ㄴ 줄 몰랐다: 예쁘다 → 예쁜 줄 몰랐다 (I didn't know she was pretty)
- Consonant stem + -은 줄 몰랐다: 작다 → 작은 줄 몰랐다 (I didn't know it was small)
- 이다 → 인 줄 몰랐다 (I didn't know it was...)
2. Action Verbs & Adjectives with 있다/없다 (Present Tense):
Use -는 줄 몰랐다.
- 가다 → 가는 줄 몰랐다 (I didn't know he was going)
- 먹다 → 먹는 줄 몰랐다 (I didn't know she was eating)
- 재미있다 → 재미있는 줄 몰랐다 (I didn't know it was fun)
3. Past Tense:
- Action Verbs: Use -ㄴ/은 줄 몰랐다. This indicates a completed action.
- 오다 (stem: 오-) + -ㄴ → 온 줄 몰랐다 (I didn't know he had come)
- 먹다 (stem: 먹-) + -은 → 먹은 줄 몰랐다 (I didn't know he had eaten) - Adjectives, 이다, 있다/없다: Use -았/었던 줄 몰랐다.
- 바쁘다 → 바빴던 줄 몰랐다 (I didn't know you had been busy)
- 있다 → 있었던 줄 몰랐다 (I didn't know it existed / there was)
4. Future Tense / Supposition (Verbs & Adjectives):
Use -ㄹ/을 줄 몰랐다.
- Vowel stem + -ㄹ 줄 몰랐다: 비가 오다 → 비가 올 줄 몰랐다 (I didn't know it would rain)
- Consonant stem + -을 줄 몰랐다: 춥다 → 추울 줄 몰랐다 (I didn't know it would be cold)
This pattern is the direct opposite of -ㄴ/는/ㄹ 줄 알았다, which means 'I thought that...' and implies a mistaken belief.
Examples (5)
- 그 영화가 그렇게 재미있는 줄 몰랐어요.
I had no idea that movie was so fun.
Word by Word: That movie so fun was I didn't know.
This uses the present tense form for adjectives ending in 있다 (재미있다 → 재미있는 줄) to express surprise about the quality of the movie.
- 민준 씨가 매일 아침 조깅하는 줄 몰랐어요.
I didn't know Minjun goes jogging every morning.
Word by Word: Minjun every morning jogs I didn't know.
This uses the present tense action verb form (조깅하다 → 조깅하는 줄) to show surprise about a current, ongoing habit.
- 어제 두 사람이 싸운 줄 몰랐네.
Oh, I didn't realize those two fought yesterday.
Word by Word: Yesterday two people fought I didn't know.
This uses the past tense action verb form (싸우다 → 싸운 줄) to express finding out about a past event.
- 오늘 시험이 이렇게 어려울 줄 몰랐어요.
I had no idea today's exam would be this difficult.
Word by Word: Today's exam this difficult would be I didn't know.
This uses the future/supposition form with an adjective (어렵다 → 어려울 줄) to express surprise about the difficulty, which was unknown before experiencing it.
- 저 분이 사장님인 줄 몰랐습니다.
I didn't know that person was the company president.
Word by Word: That person president is I didn't know.
This uses the form for nouns with 이다 (사장님이다 → 사장님인 줄).
Common Mistakes
Confusing it with -ㄴ/는지 모르다, which is for factual uncertainty.
Not Quite친구가 어디에 갔는 줄 몰라요.Better친구가 어디에 갔는지 몰라요.'-ㄴ/는/ㄹ 줄 몰랐다' expresses surprise about a fact you just learned. For simply stating you don't know information (like who, what, where, when, or whether), you should use -ㄴ/는지 모르다. The correct sentence means 'I don't know where my friend went.'
Using the wrong tense marker for the clause.
Different Meaning어제 회의가 있는 줄 몰랐어요.Better어제 회의가 있었던 줄 몰랐어요.The tense of the clause before '줄' must match the time of the event. Since the meeting was yesterday (어제), the past tense form must be used. For 있다, the correct past adnominal form is 있었던. The correct sentence means 'I didn't know there was a meeting yesterday.'
Learn This First
To express past lack of knowledge/surprise, you need knowledge patterns and past tense.
Related Patterns
- -ㄴ/는/ㄹ 줄 알았다I Thought That…, I Assumed That…
This is the direct opposite, meaning 'I thought that...' or 'I assumed that...'. It's used to express a mistaken assumption, whereas '-ㄴ/는/ㄹ 줄 몰랐다' expresses the discovery of a new, surprising fact.
- -ㄴ지/는지Whether, If
While both involve 'not knowing', -ㄴ/는지 모르다 is used for factual uncertainty (I don't know if/whether/what...), often with question words. '-ㄴ/는/ㄹ 줄 몰랐다' is about being unaware of a state or action and expressing surprise upon learning it.
- -더라고I Saw/heard/felt That
'-더라고' is used when the speaker reports something they personally observed or realized for the first time. It focuses on the act of discovery itself (e.g., '날씨가 춥더라고요' - 'I noticed the weather was cold'). '-ㄴ/는/ㄹ 줄 몰랐다' focuses more on the speaker's prior state of ignorance and their surprise.
- -는 것Thing of -ing
The -는 것 pattern is a general way to turn a verb or adjective clause into a noun phrase ('the fact that...'). '줄' in this pattern functions similarly to '것' but is specifically used in the context of knowing/not knowing or thinking/not thinking.