Pronunciation: /aɪˌkoʊ.səˈhid.rən/ Explain

Regular icosahedron
Figure 1: Regular icosahedron. Click here to see a rotating icosahedron.

An icosahedron is any 20-sided polyhedron. A regular icosahedron has congruent 20 sides, 12 vertices and 30 edges. Each side is an equilateral triangle. The Euler-Descarte formula for an icosahedron is 12 + 20 - 30 = 2. The word 'icosahedron' comes from 'icos', which is derived from the Greek word for twenty and 'hedron', which comes from the Indo-European word for seat.

A geometric net is a 2-dimensional figure that can be folded into a 3-dimensional shape. Click for a geometric net you can fold into an icosahedron.


  1. McAdams, David E.. All Math Words Dictionary, icosahedron. 2nd Classroom edition 20150108-4799968. pg 93. Life is a Story Problem LLC. January 8, 2015. Buy the book

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Cite this article as:

McAdams, David E. Icosahedron. 12/21/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. https://www.allmathwords.org/en/i/icosahedron.html.

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Revision History

12/21/2018: Reviewed and corrected IPA pronunication. (McAdams, David E.)
8/6/2018: Removed broken links, updated license, implemented new markup, implemented new Geogebra protocol. (McAdams, David E.)
2/11/2010: Added "References". (McAdams, David E.)
8/9/2008: Added More Information, information about vertices and edges, and derivation of the word. (McAdams, David E.)
6/9/2008: Initial version. (McAdams, David E.)

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