noun Etymology: Greek heptad-, heptas, from hepta Date: 1660 a group of seven

New Collegiate Dictionary. 2001.

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  • Heptad — Hep tad, n. [L. heptas the number seven. Gr. ?, ?, 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 …   The Collaborative International Dictionary of English

  • heptad — [hep′tad΄] n. [Gr heptas (gen. heptados) < hepta, SEVEN] a series or group of seven …   English World dictionary

  • heptad — /hep tad/, n. 1. the number seven. 2. a group of seven. 3. Chem. an element, atom, or group having a valence of seven. [1650 60; < Gk heptad (s. of heptás). See HEPTA , AD1] * * * …   Universalium

  • heptad — [ hɛptad] noun technical a group or set of seven. Origin C17: from Gk heptas, heptad , from hepta seven …   English new terms dictionary

  • heptad — hep•tad [[t]ˈhɛp tæd[/t]] n. 1) math. the number seven 2) math. a group of seven • Etymology: 1650–60; < Gk heptad , s. of heptás. See hepta , ad I …   From formal English to slang

  • heptad — /ˈhɛptæd/ (say heptad) noun 1. the number seven. 2. a group of seven. 3. Chemistry an element, atom, or group having a valency of seven. {Late Latin heptas, from Greek: the number seven} …   Australian English dictionary

  • heptad — noun a group of seven things …   Wiktionary

  • heptad — A septivalent chemical element or radical. * * * hep·tad (hepґtəd) any element having a valency of seven …   Medical dictionary

  • HEPTAD —    a term in chemistry to denote an atom that is the equivalent of seven atoms of hydrogen, from hepta, seven …   The Nuttall Encyclopaedia

  • heptad — n. number seven; group of seven …   English contemporary dictionary

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