n. A partition; something which divides or separates. Specificallyn. In mech.: A thin piece, generally of metal, serving as a partition, or for some other special purpose: as, the vibrating diaphragm of a telephone, for the communication of transmitted sounds, A ring, or a plate pierced with a circular hole so arranged as to fall in the axis of the instrument, used in optical instruments to cut off marginal beams of light, as in a camera or a telescope.n. In anatomy, the midriff; the museulomembranous partition which separates the thoracic from the abdominal cavity in mammals.n. In cryptogamic botany, in Equisetum, a transverse partition in the stem at the node; in Selaginella and its allies, a layer separating the prothallium from the cavity of the macrospore; in Characeæ, a constriction formed by the enveloping cells near the tip of the oögonium.n. In conchology, a septum or shelf-like plate extending into the cavity of a shell, more or less partitioning it.n. A thin ring or plate, pierced with a hole which is usually, but not always, circular.n. A sheet or disk of flexible material, confined at the edges, but free to yield to pressure on one side or the other: used in regulating-devices where pressure is one element, and to operate valves by a pressure from a distance.n. In tunnel-work, a partition separating the working-face from the first chamber.n. In statistical mechanics, a portion of space, separating two ensembles of systems of molecules, such that there is no interchange of particles between the two.n. In pathology, a membranous structure which partly or completely closes the lumen of a tube or cavity: as, inherited diaphragm of the larynx.To interpose in the path of a beam of light, or in the field of an optical instrument, a screen containing an aperture; specifically, in photography, to reduce the aperture of an objective by the use of a diaphragm.
