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

Items including scissors, light bulbs, raw eggs, rolls of tape, wooden blocks, springs, foam earplugs, jacks, tetrahedrons, and shock absorbers can all be picked up without custom programming, reports Techeblog. — Jijo Malayil, Interesting Engineering, 29 July 2026

The Tetra, from Analog Machine Works, features an unusually long tubular space frame with a pair of opposite-facing tetrahedrons in its interconnected structure. — New Atlas, 7 July 2026

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

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