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[te-truh-hee-druh n] /ˌtɛ trəˈhi drən/
noun, plural tetrahedrons, tetrahedra
[te-truh-hee-druh] /ˌtɛ trəˈhi drə/ (Show IPA)
Geometry. a solid contained by four plane faces; a triangular pyramid.
any of various objects resembling a tetrahedron in the distribution of its faces or apexes.
Origin of tetrahedron
1560-70; tetra- + -hedron, modeled on Late Greek tetráedron, noun use of neuter of tetráedros four-sided Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for tetrahedra
Historical Examples
  • The atoms are arranged in two tetrahedra with a common apex, and the relationship is maintained in the meta-body, a septet.

    Occult Chemistry

    Annie Besant and Charles W. Leadbeater
  • The globe, e, is a new form, the four tetrahedra of the proto level making a single twelve-atomed one on the meta.

    Occult Chemistry

    Annie Besant and Charles W. Leadbeater
  • The smallest particles of fire are tetrahedra, of air octahedra, of water icosahedra.

British Dictionary definitions for tetrahedra


noun (pl) -drons, -dra (-drə)
a solid figure having four plane faces. A regular tetrahedron has faces that are equilateral triangles See also polyhedron
any object shaped like a tetrahedron
Derived Forms
tetrahedral, adjective
tetrahedrally, adverb
Word Origin
C16: from New Latin, from Late Greek tetraedron; see tetra-, -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 tetrahedra



solid figure contained by four triangular surfaces, 1560s, from Late Greek tetraedron, originally neuter of tetraedros (adj.) "four-sided," from tetra- "four" + hedra "seat, base, chair, face of a geometric solid," from PIE root *sed- (1) "to sit" (see sedentary).

Online Etymology Dictionary, © 2010 Douglas Harper
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tetrahedra in Science
Plural tetrahedrons or tetrahedra
A polyhedron having four faces.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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