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heptad

[hep-tad] /ˈhɛp tæd/
noun
1.
the number seven.
2.
a group of seven.
3.
Chemistry. an element, atom, or group having a valence of seven.
Origin of heptad
1650-1660
1650-60; < Greek heptad- (stem of heptás). See hepta-, -ad1
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for heptad
Historical Examples
  • heptad, a term in chemistry to denote an atom that is the equivalent of seven atoms of hydrogen, from hepta, seven.

    The Nuttall Encyclopaedia Edited by Rev. James Wood
  • But this oddness belongs to other numbers also (pentad, heptad, &c.).

    Aristotle George Grote
British Dictionary definitions for heptad

heptad

/ˈhɛptæd/
noun
1.
a group or series of seven
2.
the number or sum of seven
3.
an atom or element with a valency of seven
Word Origin
C17: from Greek heptas seven
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Value for heptad

12
12
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