|1.||any device that shuts off, starts, regulates, or controls the flow of a fluid|
|2.||anatomy a flaplike structure in a hollow organ, such as the heart, that controls the one-way passage of fluid through that organ|
|3.||diode triode tetrode See also pentode tube, Also called: vacuum tube an evacuated electron tube containing a cathode, anode, and, usually, one or more additional control electrodes. When a positive potential is applied to the anode, electrons emitted from the cathode are attracted to the anode, constituting a flow of current which can be controlled by a voltage applied to the grid to produce amplification, oscillation, etc|
|4.||zoology any of the separable pieces that make up the shell of a mollusc|
|5.||music a device on some brass instruments by which the effective length of the tube may be varied to enable a chromatic scale to be produced|
|a. any of the several parts that make up a dry dehiscent fruit, esp a capsule|
|b. either of the two halves of a diatom cell wall|
|7.||archaic a leaf of a double door or of a folding door|
|[C14: from Latin valva a folding door]|
A membranous structure in a hollow organ or passage, as in an artery or a vein, that folds or closes to prevent the return flow of the body fluid passing through it.
Any of various devices that regulate the flow of gases, liquids, or loose materials through piping or through apertures by opening, closing, or obstructing ports or passageways.
The movable control element of such a device.
|valve (vālv) Pronunciation Key