Valve (noun)

1. A device in a pipe or container that controls the flow of a liquid or gas by opening and closing.
2. A mechanism in an internal combustion engine that controls the flow of air and fuel to the combustion chamber.

Origin:

Late middle english: from old french valve, from latin valva "a valve, gate", from valvus "hinged".

Examples:

1. He checked the valve on the gas tank.
2. The engine's valves need to be adjusted.
3. The valve on the water pipe was turned off.
4. The valve allowed for the controlled release of the gas.
5. The valve on the tire was faulty and needed to be replaced.