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octad

[ok-tad]
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noun
  1. a group or series of eight.
  2. Chemistry. an element, atom, or group having a valence of eight.

Origin of octad

1835–45; < Greek oktad- (stem of oktás) group of eight, equivalent to okt- oct- + -ad -ad1
Related formsoc·tad·ic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for octad

octad

noun
  1. a group or series of eight
  2. chem an element or group with a valency of eight
Derived Formsoctadic, adjective

Word Origin

C19: from Greek oktās, from oktō eight
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