Found 2 items, similar to tetrad.
English → English (WordNet) Definition: tetrad tetrad n : the cardinal number that is the sum of three and one [syn: four, 4, IV, quatern, quaternion, quaternary, quaternity, quartet, quadruplet, foursome, Little Joe]
English → English (gcide) Definition: Tetrad Tetrad \Tet"rad\, n. [L. tetras, -adis, Gr. ?, ?: cf. F. t['e]trade.] 1. The number four; a collection of four things; a quaternion. [1913 Webster] 2. (Chem.) A tetravalent or quadrivalent atom or radical; as, carbon is a tetrad. [1913 Webster]