What does octahedron mean?
An octahedron is a polyhedron with eight triangular faces. Its most familiar form is the regular octahedron, a symmetrical solid made from eight equilateral triangles, with twelve edges and six vertices. Octahedrons occur in geometry, mineralogy, chemistry, and crystallography, where they can describe both idealized structures and naturally occurring crystals or molecules. The word is most useful when precision matters: an octahedron is defined by its eight faces, whereas a tetrahedron has four. In mathematical usage, the plural octahedra is generally preferred, although octahedrons is also accepted in less technical contexts. The term comes from Greek roots meaning “eight” and “face” or “base,” reflecting the solid’s defining eight-faced structure.
nounA polyhedron with eight faces, all of which are triangular. A regular octahedron has eight congruent equilateral triangular faces, twelve edges, and six vertices.
- A three-dimensional polyhedron with eight faces, typically triangular; in the strict geometric sense, a regular octahedron has eight equilateral triangular faces.
"The crystal was shaped like a small, perfectly symmetrical octahedron."
"The museum displayed a glass model of an octahedron in the entrance hall."
"The mineral grew naturally in the form of a translucent octahedron."
The form octahedra is standard, especially in mathematical and scientific contexts. Octahedrons is also accepted in general usage.
"Several octahedra were arranged in a row on the shelf."
The octahedron is one of the five Platonic solids, meaning every face, edge, and vertex is arranged with perfect mathematical symmetry.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does octahedron come from?
The word combines the Greek numerical prefix okto- or oktō, meaning “eight,” with -hedron, from Greek hedra, meaning “seat,” “base,” or “face.” The term was developed in modern mathematical nomenclature to describe a polyhedron with eight faces. It belongs to a family of related geometric terms including tetrahedron, hexahedron, and other compounds formed with the same Greek elements.
Related word forms
How octahedron is actually used
The usual plural is octahedra. The form octahedrons is also accepted, especially in general writing, though octahedra is more common in mathematical and scientific usage.
Easily confused with octahedron
An octahedron has eight triangular faces, whereas a tetrahedron has four triangular faces.