잠이 잘 안 와요.

The phrase '잠이 잘 안 와요' is a combination of several Korean linguistic elements. * **잠 (jam):** This noun means 'sleep.' Its origin is rooted in Old Korean 'ᄌᆞᆷ' (cam), which has remained largely consistent in meaning over centuries. It's a fundamental word related to the human physiological need for rest. * **이 (i):** This is a subject marker. It attaches to the noun '잠' to indicate that '잠' is the subject of the sentence. Its use is grammatical and helps define the role of '잠' in the overall expression. * **잘 (jal):** This adverb means 'well' or 'properly.' It's a very common adverb used to modify verbs, indicating the manner in which an action is performed. In this context, it modifies '오다' (to come) to mean 'not coming well' or 'not happening properly.' The origin of '잘' can be traced back to Middle Korean '쟐〮' (cyal), and its core meaning has been preserved. * **안 (an):** This is a short form of negation, meaning 'not.' It is placed directly before the verb to negate the action. '안' is a very common and essential component for forming negative sentences in Korean. Its origin is ancient and has been a stable part of Korean grammar. * **와요 (wayo):** This is the conjugated form of the verb '오다' (oda), meaning 'to come.' In this specific phrase, '오다' is used idiomatically. When combined with '잠' (sleep), '잠이 오다' (jami oda) literally means 'sleep comes' or 'sleep arrives,' which is the common way to express 'to feel sleepy' or 'to fall asleep.' The '-아요/어요' ending ('-아요' in this case, due to vowel harmony with '오') is a common polite declarative ending in contemporary Korean, making the sentence polite and formal enough for general use. Therefore, '잠이 잘 안 와요' can be literally understood as 'Sleep well not comes,' or more naturally, 'Sleep doesn't come well.' This idiomatic expression perfectly conveys the difficulty in initiating or maintaining sleep. The historical stability of each component word and grammatical particle highlights the consistent and deeply rooted way Koreans have expressed this common human experience over time.