오래 is an adverb which means "for a long time", and the others are based on it. 오래간만: 오래 + 간(period, 間) + 만(since) => a long time (since last time). It is only used for the past sense. 오랜만: a contraction of 오래간만. "오래만" or "오랫만" is a wrong spelling. 오랫동안: 오래 + 동안(a period of time) => for a long while. May be used for any period of time, past or future. 오래 and 오랫동안 are adverbs, while 오래간만 and 오랜만 are nouns (add 에 to make them adverbs - 오랜만에). - 오랫동안 일기를 쓰지 않았어요. (않에요 is wrong. 않아요 is the present tense, and 않았어요 the past) - 일기를 오랫동안 [오래] 쓰지 않았어요. - 오랜만이에요 / 오래간만이에요: It's been a long time (since we met last time) - a common greeting. - 오랫동안 만나지 못해요: I can't see (you / someone) for a long time - Ok but slightly unnatural sentence. - 오래만 만나지 못해요: Wrong. 오랜만 is only used for the past. Other examples. 1) 이 음식은 참 오랜(간)만에 먹어 본다: I'm having this dish for the first time in a long while. 2) 그 사람한테선 오랫동안 소식이 없어: I haven't heard from him in a long time. 3) 할머니, 오래 사세요: Have a long life, grandma. As in 1), 오랜만 and 오래간만 are only for when something has happened again after a long hiatus. They are not interchangeable with 오래 or 오랫동안. Compare these - 나는 오랫동안 숙제를 했다: I did my homework taking a long time. - 나는 오랜만에 숙제를 했다: I've done my homework for the first time in a while. (It's been a while since I did it last time). 오래 is the most common word and can mean anything lasting long: 오래 가다 (last long), 오래 살다(live long), 오래 끌다(drag something a long time), 오래 되다(has been in existence a long time; old, aged), 오래 기다리다(wait a long time), etc.

1. 오[랫]만 = 오래간만: It's been a long time. 2. 오랫동안 = 오래: for a long time (but, 오랫동안 is likely to be used to be short period term and vice versa.) [내 친구가] [오랫동안] 일기를 쓰지 않[아요] -> My friend hasn't been keeping a daily journal for a long time. 일기를 오래만 쓰지 않에요 -> doesn't make sense at all. 오[랫]만이에요 -> It's been a long time! 오래간만이에요 -> same with above. [내 남자친구와] 오랫동안 만나지 못해요 -> I won't be able to meet [someone] for a long time [from now on] 오래만 만나지 못해요 -> doesn't make sense at all. 오래; 나는 너를 오래 보고 싶어. -> I want to keep you as my friend long.... 오래 걸려요? -> does it take a long time?

오래 일기를 쓰지 안에요 -> 오랫동안 일기를 쓰지 않았어요. 일기를 오래만 쓰지 않에요 -> ? I couldn't understand what you meant 오래만이에요 -> 오랜만이에요 오래간만이에요 -> O 오랫동안 만나지 못해요 -> 오랫동안 만나지 못해요. 오래만 만나지 못해요 -> ? I couldn't understand what you meant.