〔務め〕a duty, duties; 〔役割〕a role; 〔機能〕a function⇒やく(役)
It is the duty of parents to bring up their children.
I took on the role of father to two orphans.
This sofa serves as a bed, too.
The noun functions as an adjective in this phrase.
The doctor popped his head in at the door perfunctorily [out of sheer routine].
The nature of his office [duties] requires him to make frequent business trips abroad.