tetrahedron

noun

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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Technically, a tetrahedron is a pyramid with all four faces of the shape being triangular, including the bottom of it, as is the design of the Tetra. New Atlas, 28 Sep. 2024 The would-be tetrahedron vessel is designed to be able to carry six Tom Cruise clone passengers, as well as three Victoria clones and one Julia crew members. New Atlas, 28 Sep. 2024 The resulting shape at the center of these overlapping spheres is known as the Reuleaux tetrahedron. Max Springer, Scientific American, 7 Aug. 2024 Three-dimensional objects can be similarly modeled; for these, the FEs are usually either blocks or tetrahedra, and the number of equations is typically much higher. Manil Suri, Scientific American, 25 June 2024 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

Word History

Etymology

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 22 Dec. 2024.

Kids Definition

tetrahedron

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

More from Merriam-Webster on tetrahedron

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