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n. [ Gr. &unr_; twenty + &unr_;, combining form of &unr_; four + &unr_; seat, base. ] (Crystallog.) A twenty-four-sided solid; a tetragonal trisoctahedron or trapezohedron. [ 1913 Webster ]

{ n. Also }. [ Tetrazo- + -ine. ] (Chem.) A hypothetical compound, C2H2N4 which may be regarded as benzene with four CH groups replaced by nitrogen atoms; also, any of various derivatives of the same. There are three isomeric varieties. [ Webster 1913 Suppl. ]

‖n. pl. [ NL. See Pseudo-, and Tetramerous. ] (Zool.) A division of beetles having the fifth tarsal joint minute and obscure, so that there appear to be but four joints. -- Pseu`do*te*tram"er*al a. [1913 Webster]

[ 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 ]

n. [ Gr. &unr_; with four members; te`tra- (see Tetra-) + &unr_; limb, member. ] (Pros.) A stanza or division in lyric poetry, consisting of four verses or lines. Crabb. [ 1913 Webster ]

‖n. pl. [ NL. See Tetra-, and Corallum. ] (Paleon.) Same as Rugosa. [ 1913 Webster ]

n. (Zool.) Any species of sponge of the division Tetractinellida. Also used adjectively. [ 1913 Webster ]

‖n. pl. [ NL., from Gr. te`tra- tetra- + &unr_;, &unr_;, ray, spoke. ] (Zool.) A division of Spongiae in which the spicules are siliceous and have four branches diverging at right angles. Called also Tetractinellinae. [ 1913 Webster ]

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 ]

n. [ Gr. tetra`dymos fourfold. So named from its occurrence in compound twin crystals, or fourlings. ] (Min.) A telluride of bismuth. It is of a pale steel-gray color and metallic luster, and usually occurs in foliated masses. Called also telluric bismuth. [ 1913 Webster ]

‖n. pl. [ NL., fr. Gr. te`tra- (see Tetra-) + &unr_; power. ] (Bot.) A Linnaean class of plants having six stamens, four of which are longer than the others. [ 1913 Webster ]

n. (Bot.) A plant of the order Tetradynamia. [ 1913 Webster ]

{ } a. (Bot.) Belonging to the order Tetradynamia; having six stamens, four of which are uniformly longer than the others. [ 1913 Webster ]

n. [ L. tetragonum, Gr. tetra`gwnon; te`tra- (see Tetra-) + gwni`a corner, angle: cf. F. tétragone. ] 1. (Geom.) A plane figure having four sides and angles; a quadrangle, as a square, a rhombus, etc. [ 1913 Webster ]

2. (Astrol.) An aspect of two planets with regard to the earth when they are distant from each other ninety degrees, or the fourth of a circle. Hutton. [ 1913 Webster ]

a. 1. (Geom.) Of or pertaining to a tetragon; having four angles or sides; thus, the square, the parallelogram, the rhombus, and the trapezium are tetragonal fingers. [ 1913 Webster ]

2. (Bot.) Having four prominent longitudinal angles. [ 1913 Webster ]

3. (Crystallog.) Designating, or belonging to, a certain system of crystallization; dimetric. See Tetragonal system, under Crystallization. [ 1913 Webster ]

‖n. [ NL., fr. Gr. &unr_;; te`tra- (see Tetra-) + &unr_; a letter. ] The mystic number four, which was often symbolized to represent the Deity, whose name was expressed by four letters among some ancient nations; as, the Hebrew JeHoVaH, Greek qeo`s, Latin deus, etc. [ 1913 Webster ]

‖n. pl. [ NL., fr. Gr. te`tra- (see Tetra-) + gynh` a woman, female. ] (Bot.) A Linnaean order of plants having four styles. [ 1913 Webster ]

{ } a. (Bot.) Belonging to the order Tetragynia; having four styles. [ 1913 Webster ]

a. [ See Tetrahedron. ] 1. Having, or composed of, four sides. [ 1913 Webster ]

2. (Crystallog.) (a) Having the form of the regular tetrahedron. (b) Pertaining or related to a tetrahedron, or to the system of hemihedral forms to which the tetrahedron belongs. [ 1913 Webster ]

Tetrahedral angle (Geom.), a solid angle bounded or inclosed by four plane angles. [ 1913 Webster ]

adv. In a tetrahedral manner. [ 1913 Webster ]

n. [ So called because the crystals of the species are commonly tetrahedrons. ] (Min.) A sulphide of antimony and copper, with small quantities of other metals. It is a very common ore of copper, and some varieties yield a considerable presentage of silver. Called also gray copper ore, fahlore, and panabase. [ 1913 Webster ]

n. [ Tetra- + Gr. &unr_; seat, base, fr. &unr_; to sit. ] (Geom.) A solid figure inclosed or bounded by four triangles. [ 1913 Webster ]

☞ In crystallography, the regular tetrahedron is regarded as the hemihedral form of the regular octahedron. [ 1913 Webster ]

Regular tetrahedron (Geom.), a solid bounded by four equal equilateral triangles; one of the five regular solids. [ 1913 Webster ]

a. (Crystallog.) Pertaining to a tetrahexahedron. [ 1913 Webster ]

n. [ Tetra- + hexahedron. ] (Crystallog.) A solid in the isometric system, bounded by twenty-four equal triangular faces, four corresponding to each face of the cube. [ 1913 Webster ]

n. (Chem. & Med.) A chemical substance (C21H20O2) which is produced by the hemp plant (Cannabis sativa), and is the physiologically active agent of dried preparations of that plant, called variously marijuana, hashish, ganja, hemp, etc.; also called THC. It causes the euphoric effect for which the preparations are smoked or chewed. It is used in medicine in a purified form as an antiemetic (an antinausea agent), especially in conjunction with chemotherapy of cancer. It occurs primarily as the Δ¹-3, 4-trans isomer, also called Δ⁹-THC, with small amounts of the Δ⁶-3, 4-trans isomer detectable at about 1%. It is a controlled substance, classified as a hallucinogen, and its possession or distribution is illegal in almost all states of the United States. MI11 [ PJC ]

n. [ Gr. &unr_; four times + E. hexahedron. ] (Crystallog.) A tetrahexahedron. [ 1913 Webster ]

n. [ Tetra- + Gr. &unr_; twenty. ] (Chem.) A hydrocarbon, C24H50, resembling paraffin, and like it belonging to the marsh-gas series; -- so called from having twenty-four atoms of carbon in the molecule. [ 1913 Webster ]

n. [ Gr. &unr_;; te`tra- (see Tetra-) + &unr_; a speech, discourse: cf. F. tétralogie. ] (Gr. Drama) A group or series of four dramatic pieces, three tragedies and one satyric, or comic, piece (or sometimes four tragedies), represented consequently on the Attic stage at the Dionysiac festival. [ 1913 Webster ]

☞ A group or series of three tragedies, exhibited together without a fourth piese, was called a trilogy. [ 1913 Webster ]

‖n. pl. [ NL. See Tetramerous. ] (Zool.) A division of Coleoptera having, apparently, only four tarsal joints, one joint being rudimentary. [ 1913 Webster ]

a. [ Tetra- + Gr. &unr_; part. ] 1. (Bot.) Having the parts arranged in sets of four; as, a tetramerous flower. [ 1913 Webster ]

2. (Zool.) Having four joints in each of the tarsi; -- said of certain insects. [ 1913 Webster ]