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[ahy-koh-suh-hee-druh n, ahy-kos-uh-] /aɪˌkoʊ səˈhi drən, aɪˌkɒs ə-/
noun, plural icosahedrons, icosahedra
[ahy-koh-suh-hee-druh, ahy-kos-uh-] /aɪˌkoʊ səˈhi drə, aɪˌkɒs ə-/ (Show IPA)
a solid figure having 20 faces.
Origin of icosahedron
1560-70; < Greek eikosáedron, equivalent to eikosa- (variant of eikosi-, combining form of eíkosi twenty) + -edron -hedron
Related forms
icosahedral, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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British Dictionary definitions for icosahedron


noun (pl) -drons, -dra (-drə)
a solid figure having 20 faces. The faces of a regular icosahedron are equilateral triangles
Derived Forms
icosahedral, adjective
Word Origin
C16: from Greek eikosaedron, from eikosi twenty + -edron-hedron
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 Origin and History for icosahedron

1560s, from Greek eikosahedron, neuter of eikosahedros, from eikosi "twenty" + -hedra "seat, base, chair, face of a geometric solid," from PIE root *sed- (1) "to sit" (see sedentary). Greek eikosi is from PIE *wikmti- "twenty," from *wi- "in half," hence "two" + (d)kmti-, from root *dekm- "ten" (see ten).

Online Etymology Dictionary, © 2010 Douglas Harper
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icosahedron in Science

Plural icosahedrons or icosahedra
A polyhedron having twenty faces.

icosahedral adjective
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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