tet·​ra·​he·​dron ˌte-trə-ˈhē-drən How to pronounce tetrahedron (audio)
plural tetrahedrons or tetrahedra ˌte-trə-ˈhē-drə How to pronounce tetrahedron (audio)
: a polyhedron that has four faces

Illustration of tetrahedron

Illustration of tetrahedron

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 The stack of twisting, growing tetrahedra — a nod to nonlinear scientific advancement — looms, 42 feet high, like a sphinx. Megan Molteni, STAT, 14 Mar. 2023 Five years ago, at age 94, Fromson awarded a grant through his philanthropic foundation to the University of Connecticut to determine if a tetrahedron packed with different elements could improve the durability of the undersides of U.S. Humvees in Iraq. Kenneth R. Gosselin, courant.com, 28 June 2021 One group started chipping away at the foam volleyballs while another set about taping together basketballs into a tetrahedron. IEEE Spectrum, 16 Nov. 2020 Mold that box into a pyramid or tetrahedron or any other everyday polyhedron. Devin Powell, Discover Magazine, 20 Mar. 2019 That extraordinary hardness arises from a strong and inflexible structure: Five atoms form a tetrahedron and share electron pairs with each other. Gemma Tarlach, Discover Magazine, 5 Apr. 2018 Many elements overlapped, forming a multidimensional sculpture: a triangle might jut out of a tetrahedron and meet another triangle at a point. Kelsey Houston-Edwards, Scientific American, 21 Sep. 2022 If the regular tetrahedron doesn’t tile space, the question becomes: Do any tetrahedra? Quanta Magazine, 9 Feb. 2021 Triangles and tetrahedra are examples of more general shapes called simplices, which can be defined in any dimension. Quanta Magazine, 13 Jan. 2015

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'tetrahedron.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


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

First Known Use

1570, in the meaning defined above

Time Traveler
The first known use of tetrahedron was in 1570

Dictionary Entries Near tetrahedron

Cite this Entry

“Tetrahedron.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tetrahedron. Accessed 23 Jun. 2024.

Kids Definition


tet·​ra·​he·​dron ˌte-trə-ˈhē-drən How to pronounce tetrahedron (audio)
plural tetrahedrons or tetrahedra
: a polyhedron that has four faces

More from Merriam-Webster on tetrahedron

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