DIFFERENTIALE, in the higher geometry, an infinitely small quantity, or a particle of quantity so small as to be less than any assignable one. It is called a differential, or differential quantity, because frequently considered as the difference of two quantities; and, as such, is the foundation of the differential calculus: Sir Isaac Newton, and the English, call it a moment, as being considered as the momentary increase of quantity. See FLUXIONS.

DIEXAHEDRIA, in natural history, a genus of pellucid and crystalliform spars, composed of two pyramids, joined base to base, without any intermediate column: the diexahedra are dodecahedral, or composed of two hexangular pyramids.