tet·​ra·​he·​dron | \ ˌte-trə-ˈhē-drən How to pronounce tetrahedron (audio) \
plural tetrahedrons or tetrahedra\ ˌte-​trə-​ˈhē-​drə How to pronounce tetrahedra (audio) \

Definition of tetrahedron

: a polyhedron that has four faces

Illustration of tetrahedron

Illustration of tetrahedron

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Did You Know?

The simplest tetrahedron is made of four equal-sided triangles: one is used as the base, and the other three are fitted to it and each other to make a pyramid. But the great pyramids of Egypt aren't tetrahedrons: they instead have a square base and four triangular faces, and thus are five-sided rather than four-sided.

Examples of tetrahedron in a Sentence

Recent Examples on the Web Triangles and tetrahedra are examples of more general shapes called simplices, which can be defined in any dimension. Quanta Magazine, "A Proof That Some Spaces Can’t Be Cut," 13 Jan. 2015 That extraordinary hardness arises from a strong and inflexible structure: Five atoms form a tetrahedron and share electron pairs with each other. 3. Gemma Tarlach, Discover Magazine, "20 Things You Didn't Know About ... Diamonds," 23 Mar. 2018 With eight modules of tetrahedrons (triangular pyramids) made of translucent polyethelene and aluminum tubes that billow out from a symmetrical axis, the piece feels both organic and machinelike. Molly Glentzer, Houston Chronicle, "Bloated, full of hot air: Sergio Prego's art mimics society," 10 Jan. 2018 They are defined by symmetry, and the Greeks knew that there were only five possibilities meeting the criteria: the tetrahedron, cube, octahedron, dodecahedron and icosahedron. Eugenia Cheng, WSJ, "Lessons of the Möbius Bagel," 10 Aug. 2017 The new metropolis would consist of a giant tetrahedron—a pyramid made of equilateral triangles—a shape that Fuller, the popularizer of the geodesic dome, admired for its stability and symmetry. Rachel Riederer, New Republic, "Libertarians Seek a Home on the High Seas," 29 May 2017 As Mars cooled internally and shrank, some faces of the martian tetrahedron slumped. David S. F. Portree, WIRED, "Mars: A World for Exploration (1959)," 8 May 2012

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'tetrahedron.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of tetrahedron

1570, in the meaning defined above

History and Etymology for tetrahedron

New Latin, from Late Greek tetraedron, neuter of tetraedros having four faces, from Greek tetra- + hedra seat, face — more at sit

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Time Traveler for tetrahedron

Time Traveler

The first known use of tetrahedron was in 1570

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Cite this Entry

“Tetrahedron.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tetrahedron. Accessed 29 Nov. 2020.

More from Merriam-Webster on tetrahedron

Britannica.com: Encyclopedia article about tetrahedron

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