[ See Seven. ] A combining form from Gr. "epta`, seven. [1913 Webster]

n. [ Gr. "epta`chordos seven-stringed; "epta` seven + chordh` chord: cf. F. heptacorde. See Seven, and Chord. ] 1. (Anc. Mus.) (a) A system of seven sounds. (b) A lyre with seven chords. [ 1913 Webster ]

2. (Anc. Poet.) A composition sung to the sound of seven chords or tones. Moore (Encyc. of Music). [ 1913 Webster ]

n. [ L. heptas the number seven. Gr. &unr_;, &unr_;, fr. "epta` seven.] (Chem.) An atom which has a valence of seven, and which can be theoretically combined with, substituted for, or replaced by, seven monad atoms or radicals; as, iodine is a heptad in iodic acid. Also used as an adjective. [1913 Webster]

n. [ Cf. F. heptade. See Heptad. ] The sum or number of seven. [ 1913 Webster ]

n. [ Gr. &unr_;; "epta` seven + 3, &unr_;, tongue, language.] A book in seven languages. [1913 Webster]

n. [ Gr. &unr_; sevencornered; "epta` seven + &unr_; angle: cf. F. heptagone.] (Geom.) A plane figure consisting of seven sides and having seven angles. [1913 Webster]

a. [ Cf. F. heptagonal. ] Having seven angles or sides. [ 1913 Webster ]

Heptagonal numbers (Arith.), the numbers of the series 1, 7, 18, 34, 55, etc., being figurate numbers formed by adding successively the terms of the arithmetical series 1, 6, 11, 16, 21, etc. [ 1913 Webster ]

‖n. pl. [ NL., fr. Gr. "epta` seven + &unr_; woman, female: cf. F. heptagunie.] (Bot.) A Linnaean order of plants having seven pistils.

{ } a. [ Cf. F. heptagyne. ] (Bot.) Having seven pistils. [ 1913 Webster ]

n. [ Hepta- + Gr. &unr_; seat, base, fr. &unr_; to sit: cf. F. heptaèdre. ] (Geom.) A solid figure with seven sides. [ 1913 Webster ]

a. [ Hepta- + Gr. &unr_; part. ] (Bot.) Consisting of seven parts, or having the parts in sets of sevens. Gray. [ 1913 Webster ]

‖n. pl. [ NL., fr. Gr. "epta` seven + &unr_;, &unr_;, man, male: cf. F. heptandrie.] (Bot.) A Linnaean class of plants having seven stamens.

{ } a. [ Cf. F. heptandre. ] (Bot.) Having seven stamens. [ 1913 Webster ]

n. [ Gr. "epta` seven.] (Chem.) Any one of several isometric hydrocarbons, C7H16, of the paraffin series (nine are possible, four are known); -- so called because the molecule has seven carbon atoms. Specifically, a colorless liquid, found as a constituent of petroleum, in the tar oil of cannel coal, etc. [1913 Webster]

a. [ Hepta- + angular: cf. F. heptangulaire. Cf. Septangular. ] Having seven angles. [ 1913 Webster ]

a. [ Hepta- + Gr. &unr_; leaf: cf. F. heptaphylle. ] (Bot.) Having seven leaves. [ 1913 Webster ]

n. Same as Heptarchist. [ 1913 Webster ]

a. [ Cf. F. heptarchique. ] Of or pertaining to a heptarchy; constituting or consisting of a heptarchy. T. Warton. [ 1913 Webster ]

n. A ruler of one division of a heptarchy. [ Written also heptarch. ] [ 1913 Webster ]

n. [ Hepta- + -archy: cf. F. heptarchie. ] A government by seven persons; also, a country under seven rulers. [ 1913 Webster ]

☞ The word is most commonly applied to England, when it was divided into seven kingdoms; as, the Saxon heptachy, which consisted of Kent, the South Saxons (Sussex), West Saxons (Wessex), East Saxons (Essex), the East Angles, Mercia, and Northumberland. [ 1913 Webster ]

a. [ Hepta- + Gr. &unr_; a seed. ] (Bot.) Having seven seeds. [ 1913 Webster ]

n. [ Hepta- + Gr. sti`chos line, verse. ] (Pros.) A composition consisting of seven lines or verses. [ 1913 Webster ]

n. [ L. heptateuchos, Gr. "epta` seven + &unr_; tool, book; &unr_; to prepare, make, work: cf. F. heptateuque.] The first seven books of the Testament. [1913 Webster]

a. [ Hepta- + L. valens, p. pr. See Valence. ] (Chem.) Having seven units of attractive force or affinity; -- said of heptad elements or radicals. [ 1913 Webster ]