[ahy-koh-suh-hee-druh n, ahy-kos-uh-]
noun, plural i·co·sa·he·drons, i·co·sa·he·dra [ahy-koh-suh-hee-druh, ahy-kos-uh-] /aɪˌkoʊ səˈhi drə, aɪˌkɒs ə-/.
  1. 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 formsi·co·sa·he·dral, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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Historical Examples of icosahedron

British Dictionary definitions for icosahedron


noun plural -drons or -dra (-drə)
  1. a solid figure having 20 faces. The faces of a regular icosahedron are equilateral triangles
Derived Formsicosahedral, adjective

Word Origin for icosahedron

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

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

icosahedron in Science


Plural icosahedrons icosahedra
  1. A polyhedron having twenty faces.
Related formsicosahedral adjective
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.