■ noun
1》 a device for controlling the passage of fluid through a pipe or duct, especially an automatic device which allows movement in one direction only.
2》 a cylindrical mechanism to vary the effective length of the tube in a brass musical instrument.
3》 Anatomy & Zoology a membranous fold in an organ or vessel which allows blood or other fluid to flow in one direction.
4》 Zoology each of the halves of the hinged shell of a bi~ mollusc or brachiopod.
5》 Botany each of the halves or sections into which a dry fruit dehisces.
Derivatives
~d adjective
~less adjective
Origin
ME (denoting a leaf of a folding or double door): from L. valva .