"(으)ㄴ 지" and "(으)ㄴ/는지" 1. -(으)ㄴ 지 지 is a dependent noun here meaning the time since some event or action. It is always used with a verb representing an action. E.g. 저는 한국에 온 지 2년이 되었습니다 = It's been two years since I came to Korea. E.g. 컴퓨터 게임을 한 지 5 시간이 넘었어요 = It's been more than five hours since I started playing the computer game. * The verb before 지 should be in the -(으)ㄴ form, which acts as an attributive adjective in the past tense (과거) indicating the result of an action. It cannot use the -는 form (explained below) which is used for the other sense of -지. 2. -(으)ㄴ지, -는지 (and also -(으)ㄹ지) -지 (a verb ending form) turns a verb phrase into a noun phrase, adding the sense of "if" or "whether" or "that". It is used to express wondering about or questioning something, usually with words like 알다, 모르다, 기억하다, 생각나다, etc. E.g. 저 분이 누구인지 모르겠어요 = I'm not sure who that person is. E.g. 이거 어떻게 만들었는지 가르쳐 주세요 = Please show me how you made this. E.g. (내) 답이 틀렸을지도 모르겠다 = My answer might have been wrong. The difference between the three forms has to do with the tense. It's a big subject, but here's a short intro. A. -는지 = present tense of verbs. (this form can't be used with adjectives) E.g. 개가 왜 짖는지 모르겠어 (I don't know why the dog is barking). B. -(아/어)ㅆ는지 = past tense of verbs or adjectives. E.g. 개가 왜 짖었는지 모르겠어 = I don't know why the dog barked. (verb) E.g. 지난 겨울엔 얼마나 추웠는지 몰라 = How freezing cold it was last window. (adjective) C. -(으)ㄴ지 = present tense of adjectives. E.g. 누가 옳은지는 두고보면 안다 = Time will soon tell who's right. D. -(으)ㄹ지 = future tense, or a possible imaginary situation (subjunctive-like). E.g. 이렇게 될지 아무도 몰랐다 = No one knew it would turn out this way (future event as viewed from the past) E.g. 될지 안 될지 해 봐야 한다 = We should give it a try to see whether it will work or not. These are derived from the more general tense forms, so you you should study verb/adjective tenses in general to fully understand them.