word-forming element meaning "within, inside, on the inside," from Latin preposition intra "on the inside, within, in, into;" of time, "during, in the course of," related to inter "between," from PIE *en-t(e)ro-, from root *en "in." Commonly opposed to extra-, and compare inter-. The use of intra as a prefix was rare in classical Latin.
1753, "consisting of or resembling cells," with reference to tissue, from Modern Latin cellularis "of little cells," from cellula "little cell," diminutive of cella "small room" (see cell). Of mobile phone systems (in which the area served is divided into "cells" of a few square miles served by transmitters), 1977. Related: Cellularity.