The way in which a machine or other thing performs or functions
In action or full operation
It's what keeps the hospital functioning, so we can treat everyone who comes this way.
Regarding disorders and disabilities: We should be able to repair, heal, or replace any part of the body not functioning at the level the person with the disability reasonably wishes it to.
I remember in autumn of '87 thinking it was perfectly reasonable to take the red 1964 Corvair convertible for a test drive, despite its lack of functioning brakes.
In a few cases some of the tracheids have very thick walls and reduced cavities, functioning as mechanical rather than as waterconducting elements.
The whole functioning of our mental apparatus is directed upon yielding the right response to the stimulations of the environment, and is valuable if and in so far as it does this.