What does octahedra mean?
Octahedra is the plural of octahedron, a polyhedron with eight triangular faces. The singular name comes from the Greek roots for “eight” and “base” or “seat,” reflecting the shape's eight-faced structure. In geometry, octahedra are especially important because a regular octahedron can be formed by joining two square-based pyramids at their bases. They also occur throughout crystallography, chemistry, and materials science, where arrangements of octahedra describe the geometry of atoms, ions, or structural units. The word is normally used with a determiner or number, as in “two octahedra,” and the plural octahedra is preferred in mathematical writing, although octahedrons is also found in general use.
nounThe plural of octahedron: polyhedra each having eight triangular faces.
- Plural of octahedron, referring to polyhedra with eight triangular faces.
"The model consists of four interlocking octahedra."
"The crystal structure contains linked octahedra."
"Students constructed several octahedra from folded paper."
The standard mathematical plural is octahedra, although octahedrons is also encountered.
"The compound is built from eight regular octahedra."
Eight triangular faces meet at the vertices of an octahedron, making it one of the most recognizable shapes in geometry.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does octahedra come from?
The singular octahedron comes from New Latin octahedron, from Greek oktáedron, a term associated with okto, “eight,” and hedra, “base” or “seat.” Its plural form octahedra follows the usual Latin plural pattern. Other English words sharing the same numerical root include octagon, octagonal, octet, and octave, all ultimately connected with the concept of eight.
Related word forms
How octahedra is actually used
The regular plural is octahedra; octahedrons is also encountered, but octahedra is the preferred form in formal mathematical and scientific usage.
Easily confused with octahedra
An octahedron is the singular form, while octahedra is the standard plural.