- A device for controlling the passage of fluid through a pipe or duct, esp. an automatic device allowing movement in one direction only
- (valve) control consisting of a mechanical device for controlling the flow of a fluid
- (valve) a structure in a hollow organ (like the heart) with a flap to insure one-way flow of fluid through it
- A cylindrical mechanism in a brass instrument that, when depressed or turned, admits air into different sections of tubing and so extends the range of available notes
- (valve) device in a brass wind instrument for varying the length of the air column to alter the pitch of a tone
- A membranous fold in a hollow organ or tubular structure, such as a blood vessel or the digestive tract, that maintains the flow of the contents in one direction by closing in response to any pressure from reverse flow