昼夜
zhoù yè · HSK 7
day and night
☀️🌙 昼 = daytime + 夜 = night; together day-and-night, around the clock
昼 means daytime and 夜 means night, so 昼夜 stacks the two halves of a full 24-hour cycle. Used to say something runs continuously, without stop, day and night.
夜 — 亠 lid + 亻 person + 夕 evening moon
夜 originally depicted a person (亻) under a roof (亠) with the moon (夕) beside them, evoking nighttime rest. The moon component 夕 carries the meaning of evening, while the surrounding elements set the scene of a person at night. Over time it came to mean 'night' in general.