tetrahedron

noun

tet·​ra·​he·​dron ˌte-trə-ˈhē-drən 

plural tetrahedrons or tetrahedra ˌte-trə-ˈhē-drə 

: a polyhedron that has four faces

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

Convex shapes exist in higher-dimensional space, too, like the three-dimensional tetrahedron. — Joseph Howlett, Scientific American, 19 May 2026

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

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

Rhymes for tetrahedron

• octahedron
• polyhedron
• dodecahedron
• icosahedron
• sanhedrin

Kids Definition

tetrahedron

noun

tet·​ra·​he·​dron ˌte-trə-ˈhē-drən 

plural tetrahedrons or tetrahedra

-drə

: a polyhedron that has four faces

tetrahedral

-drəl

adjective