the number four.-a set of four parts, things, or person; four things taken collectively; a group of four words, phrases, circumstances, facts, or the like.-a word of four syllables; a quadrisyllable.-the quotient of two vectors, or of two directed right lines in space, considered as depending on four geometrical elements, and as expressible by an algebraic symbol of quadrinomial form.-to divide into quaternions, files, or companies.