밤새, 밤새워, 하룻밤 * 하룻밤(n) - a night. Usually means the duration of the night, and more rarely a certain night (어느 날 밤). * 밤새워(adv) - -아/어 conjugation of 밤새우다 (short form of 밤을 새우다], "to stay up through the night". It can also be an imperative form since the -아/어 ending functions as such. * 밤새 can mean a few things, as both 사이 and 새워 can shorten to 새. 1. 밤사이(n) - 밤 + 사이 (time between two points; time elapsed) = 밤 동안, "the time of the night". This usage is rare. 2. 밤사이에(adv) - '에' (at, in, during) is often dropped, so 밤새 usually means 밤사이에, or "during the night". 3. 밤새우다(v) - 밤(을) 새우다 is often said as 밤새다 in speech. So 밤새 can mean 밤새워 as explained above. 4. 밤이 새다 - 새다(vi) means the night passes and the day dawns. So 밤이 새다 means the day breaks, or 날이 밝다. This meaning is often expressed as 밤새도록 (밤이 새도록 = till the day breaks = all night long). So there are many variations of 밤새, but they all evolve around the related verbs 새우다(vt) and 새다(vi)), and to a lesser extent around the noun 사이. What's tricky is that 새우다 often shortens to 새다 in speech, which may be confusing to learners. Examples. - 하룻밤 동안에 서울서 네 건의 화재가 발생했다 = Four fire incidents broke out in Seoul in just one night. - 공부할 게 많아서 밤새워 해도 못 끝내겠다 = There's so much to study it appears I won't be done if I spend all night. - 밤새 [밤사이에] 비가 많이 왔다 = It rained a lot during the night. - 왜 얼굴이 그래? 밤샜냐 [밤새웠냐, 밤을 새웠냐]? = Why do you look like that? Did you stay up all night? - 일이 많아 밤새 [밤새도록, 밤이 새도록] 해도 못 하겠다 = There's so much to do I won't be done even if I work until morning.