octahedron
/ˌɒktəˈhiːdrən
/noun (plural octahedra /ˌɒktəˈhiːdrə/ or octahedrons)
1A three-dimensional shape having eight plane faces, especially a regular solid figure with eight equal triangular faces.These are often known as the Platonic solids: the tetrahedron, cube, octahedron, dodecahedron and icosahedron....
- These five remarkable solids - tetrahedron, cube, octahedron, dodecahedron, icosahedron - have faces that are congruent equilateral polygons.
- Plato believed that atoms have the shapes of regular polyhedra: cubes, tetrahedrons, octahedrons, and so on.
1.1A body, especially a crystal, in the form of a regular octahedron.Earth was a cube, air an octahedron, fire a tetrahedron and water an icosahedron....
- The fluorite tends to occur only as cubes modified by the dodecahedron, with simple cubes or octahedra uncommon or absent.
- Water was an icosahedron, and air had to be an octahedron.
Derivatives
octahedral
/ adjective ...- It's octahedral in shape with a high, vaulted ceiling and sunlight streaming through hidden windows.
- The outer portion of the garnets is altered to clinochlore, and small octahedral crystals of magnetite and martite occur in the schist.
- In 1990 bright emerald-green, transparent, octahedral fluorite crystals were discovered in the Kettle mine by mine surveyor Michelle Scott.
Origin
Late 16th century: from Greek oktaedron, neuter (used as a noun) of oktaedros 'eight-faced'.