valve
noun
[ valv ]
• a device for controlling the passage of fluid or air through a pipe, duct, etc., especially an automatic device allowing movement in one direction only.
• "a valve shuts off the flow from the boiler when the water is hot enough"
• each of the halves of the hinged shell of a bivalve mollusc or brachiopod, or of the parts of the compound shell of a barnacle.
Origin:
late Middle English (denoting a leaf of a folding or double door): from Latin valva .
