[ Gr. te`tra-, from te`sares, te`ttares, four. See Four. ] 1. A combining form or prefix signifying four, as in tetrabasic, tetrapetalous. [ 1913 Webster ]

2. (Chem.) A combining form (also used adjectively) denoting four proportional or combining parts of the substance or ingredient denoted by the term to which it is prefixed, as in tetra-chloride, tetroxide. [ 1913 Webster ]

a. [ Tetra- + basic. ] (Chem.) Capable of neutralizing four molecules of a monacid base; having four hydrogen atoms capable of replacement by bases; quadribasic; -- said of certain acids; thus, normal silicic acid, Si(OH)4, is a tetrabasic acid. [ 1913 Webster ]

a. [ Tetra- + boric. ] (Chem.) Same as Pyroboric. [ 1913 Webster ]

‖n. pl. [ NL. See Tetra-, and Branchia. ] (Zool.) An order of Cephalopoda having four gills. Among living species it includes only the pearly nautilus. Numerous genera and species are found in the fossil state, such as Ammonites, Baculites, Orthoceras, etc. [ 1913 Webster ]

a. [ Tetra + branchiate. ] (Zool.) Of or pertaining to the Tetrabranchiata. -- n. One of the Tetrabranchiata. [ 1913 Webster ]

a. [ Tetra- + carpellary. ] (Bot.) Composed of four carpels. [ 1913 Webster ]

n. [ L. tetrachordon, Gr. &unr_;, from &unr_; four-stringed; te`tra- (see Tetra-) + &unr_; a chord: cf. F. tétrachorde. ] (Anc. Mus.) A scale series of four sounds, of which the extremes, or first and last, constituted a fourth. These extremes were immutable; the two middle sounds were changeable. [ 1913 Webster ]

a. [ Gr. te`tracha in four parts + te`mnein to cut. ] (Bot.) Having a division by fours; separated into four parts or series, or into series of fours. [ 1913 Webster ]

a. [ Tetra + acid. ] (Chem.) Capable of neutralizing four molecules of a monobasic acid; having four hydrogen atoms capable of replacement ba acids or acid atoms; -- said of certain bases; thus, erythrine, C4H6(OH)4, is a tetracid alcohol. [ 1913 Webster ]

a. [ See Tetra-, and Coccus. ] (Bot.) Having four cocci, or carpels. [ 1913 Webster ]