noun, noun which may take the genitive case particle 'no'
off duty; not on duty
Used for police officers, firefighters, guards, and other shift workers to indicate they are not currently on duty. Often used as a noun or with の to modify another noun.
今日は非番なので、家でゆっくりします。
I'm off duty today, so I'll relax at home.
非番の警官が事件に遭遇した。
An off-duty police officer encountered the incident.