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~(으)ㄴ/는/(으)ㄹ 줄 몰랐다(알았다):

• Expresses the realization of an incorrect assumption
• Equivalent to “I hadn’t realized” or “I had thought”

Tenses:

Adjectives:

• 과거: ~(으)ㄴ 줄 몰랐다/알았다
• 추측: ~(으)ㄹ 줄 몰랐다/알았다

Verbs:

• 과거: ~(으)ㄴ 줄 몰랐다/알았다
• 현재: ~는 줄 몰랐다/알았다
• 미래/추측: ~(으)ㄹ 줄 몰랐다/알았다

Noun이다:

• 과거: ~이었는/였는 줄 몰랐다/알았다
• 현재: ~인 줄 몰랐다/알았다
• 추측: ~일 줄 몰랐다/알았다

Examples:

과거:

• A: 톰크루즈는 그렇게 키가 작은 줄 몰랐어요.
  (I didn’t know Tom Cruise was that short.)
• V: 어제는 비가 온 줄 알았어요.
  (I had thought it was going to rain yesterday.)
• N: 당신의 집과 차를 보니까 부자 였는 줄 알았어요.
  (I saw your house and your car, so I thought you were rich.)
• A: 검은색 옷을 산 줄 몰랐어요.
  (I didn’t know you bought a black shirt.)
• V: 숙제를 한 줄 알았어요.
  (I had thought we had homework.)

현재:

• V: 지금 출근하는 줄 알았어요.
  (I thought it was time to start work now.)
• N: 컴퓨터 프로그램머인 줄 몰랐어요.
  (I didn’t know that was a computer program.)
• V: 그렇게 디자인하는 줄 몰랐어요.
  (I didn’t you could design like that.)
• N: 영어 선생님인 줄 알았어요.
  (I thought you were an English teacher.)
• V: 그렇게 시끄러운 이야기하는 줄 몰랐어요.
  (I didn’t know it was such a noisy story.)

미래/추측:

• A: 너의 남자친구가 이렇게 못생길 줄 알았어요.
  (I thought your boyfriend would be ugly like this.)
• V: 이상한 남자들이 화장실 안에서 담배를 피울 줄 몰랐어요.
  (I hadn’t realized that strange boys like to smoke in the bathrooms.)
• N: 당신이 이상한 남자일 줄 몰랐어요.
  (I didn’t know you were a strange guy.)
• A: 그분은 평범할 줄 알았어요.
  (I thought he would be an ordinary guy.)
• V: 항상 밖에 나가서 담배 피워야 하는 줄 알았어요.
  (I thought you should always go outside to smoke a cigarette.)

**These are notes from Korean Grammar in Use: Intermediate. For more in-depth explanations, buy the book.

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