n. [ L. tetras, -adis, Gr. &unr_;, &unr_;: cf. F. tétrade. ] 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 ]

{ } a. [ Cf. F. tétradactyle. ] (Zool.) Tetradactylous. [ 1913 Webster ]

a. [ Gr. &unr_;; te`tra- (see Tetra-) + &unr_; finger, toe. ] (Zool.) Having, or characterized by, four digits to the foot or hand. [ 1913 Webster ]

n. [ Tetra- + Gr. &unr_; ten. ] (Chem.) A light oily hydrocarbon, C14H30, of the marsh-gas series; -- so called from the fourteen carbon atoms in the molecule. [ 1913 Webster ]

‖n. pl. [ NL. See Tetra-, and Decapoda. ] (Zool.) Same as Arthrostraca. [ 1913 Webster ]

a. (Chem.) Of or pertaining to a tetrad; possessing or having the characteristics of a tetrad; as, a carbon is a tetradic element. [ 1913 Webster ]

n. [ See Tetrad. ] A person in some way remarkable with regard to the number four, as one born on the fourth day of the month, or one who reverenced four persons in the Godhead. Smart. [ 1913 Webster ]

n. (Zool.) See Tetrodon. [ 1913 Webster ]

a. & n. (Zool.) See Tetrodont. [ 1913 Webster ]

{ ‖ } n. [ NL. tetradrachma, fr. Gr. tetra`drachmon; te`tra- (see Tetra-) + drachmh` drachm, drachma. ] A silver coin among the ancient Greeks, of the value of four drachms. The Attic tetradrachm was equal to 3s. 3d. sterling, or about 76 cents. [ 1913 Webster ]