also: よばん
noun
night watch; night sentry
Refers to the duty or person keeping watch at night, often in a guard or security context.
夜番の仕事は眠気との戦いだ。
Working the night watch is a battle against drowsiness.
彼は毎晩、夜番として倉庫を見回っている。
Every night, he patrols the warehouse as a night sentry.
夜警 is a more formal term for night guard or night patrol, often used in official contexts, while 夜番 is a common, everyday word for night watch duty.
Compound of 夜 (night) and 番 (watch, guard). The reading やばん uses the on'yomi of both characters, while よばん uses the kun'yomi for 夜 and on'yomi for 番.