noun, noun or participle which takes 'suru', intransitive verb
night duty; night watch; night shift
Refers to staying overnight at a workplace (e.g., office, hospital, school) to be on duty or stand guard. Often used in institutional settings.
今夜は宿直なので、家に帰れません。
I'm on night duty tonight, so I can't go home.
宿直の先生が校内を見回っている。
The teacher on night duty is patrolling the school.