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A group or sequence of eight.

[Greek oktas, oktad-, from oktō, eight; see oktō(u) in Indo-European roots.]

oc·tad′ic adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


1. (Mathematics) a group or series of eight
2. (Chemistry) chem an element or group with a valency of eight
[C19: from Greek oktās, from oktō eight]
ocˈtadic adj
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈɒk tæd)

1. a group or series of eight.
2. an element, atom, or group having a valence of eight.
[1835–45; < Greek oktad- (s. of oktás) group of eight =okt(ṓ) eight + -ad -ad1]
oc•tad′ic, adj.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.octad - the cardinal number that is the sum of seven and oneoctad - the cardinal number that is the sum of seven and one
digit, figure - one of the elements that collectively form a system of numeration; "0 and 1 are digits"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in periodicals archive ?
The latter GQ contained a g-u octad in addition to guanine and adenine tetrads [135].
Octad pollen formation in Cymbopetalum (Annonaceae): the binding mechanism.
The algorithm will therefore choose the best octad from those few available.
The patient underwent the implantation of 8-contact-compact-lead percutaneously sensor rechargeable battery (2 x 8 octad leads, model #3778-75 Medtronic Co.).
Bilateral Quad electrode leads were subcutaneously placed in the posterior temporal region along with a single Octad electrode lead placed subcutaneously around the C2 vertebral level (Figure 1).
YESTERDAY'S SOLUTION: actin; action; anodic; antic; atonic; attic; canid; cant; canto; cation; ciao; citation; coati; coda; coin; cotta; dacoit; diatonic; dicTATION; diction; icon; indict; intact; octad; octant; ontic; otic; tacit; taco; titanic; tonic.