Tetrad
Pronunciation : Tet"rad
Part of Speech : n.
Etymology : [L. tetras, -adis, Gr. t?trade.]
Definition : 1. The number four; a collection of four things; a quaternion.
2. (Chem.)
Defn: A tetravalent or quadrivalent atom or radical; as, carbon is a tetrad.
Source : Webster's Unabridged Dictionary, 1913