Definition of octahedron in English:


nounoctahedra, 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.’
    • ‘A dodecahedron modified by the octahedron and cube from Nordmark, Sweden, is figured in Goldschmidt.’
    • ‘It was a set of platonic bodies: there was an octahedron and a double tetrahedron.’
    • ‘Theaetetus was the first to study the octahedron and the icosahedron and it is believed that Book XIII of Euclid's Elements is based on his work.’
    • ‘This six-point perspective, with the six vertices of an octahedron serving as the vanishing points, becomes the basis of his spherical paintings.’
    • ‘I'd like to mention in passing that the octahedron, the dual of the cube, also contains 26: 8 faces, 12 edges, 6 vertices.’
    • ‘Finally, the octahedron inscribed in the Venus-orbit sphere has itself an inscribed sphere, on which the orbit of Mercury lies.’
    • ‘There is the octahedron, with 8 faces, 12 edges and 6 vertices.’
    • ‘The cube, consisting of six square faces, is a common form either alone or in combination with other forms, especially the octahedron.’
    • ‘Peterson and Jordan go on to investigate interesting links between integer octahedra and integer antiprisms.’
    1. 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.’
      • ‘The octahedra range from 5 to 10 pm in diameter and show interpenetrant growth.’
      • ‘The exception is an octahedron from another Peruvian mine, Quiruvilca (400 kilometers north of Huanzala).’
      • ‘It involves placing the knot inside a plastic octahedron and mapping where the strands of the knot meet.’
      • ‘Older collections sometimes contain small, very pale, transparent green fluorite octahedra from the Tomboy vein.’
      • ‘She notes that lime-green to purplish-green modified fluorite octahedra have been found at this pegmatite.’
      • ‘One small lot of specimens from Alta Floresta, Mato Grosso, exhibited moderately rounded, well-developed octahedra.’
      • ‘The Ogluinsky mine specimens are millimeter-sized octahedra, and the Nicolay mine specimens are unabraded and have mica attached.’
      • ‘Most that I have seen have been elongated octahedra or other forms, such as some of the branches of an arborescent aggregate.’
      • ‘The one exception is the exciting accidental discovery of a 4.22-carat, gem-quality octahedron in Dale County, Alabama.’
      • ‘One specimen was covered with small rounded crystal-like projections, similar to cube and octahedron forms.’
      • ‘When well-crystallized, it typically exhibits the cube form modified by the octahedron and dodecahedron; crystals to 20 cm across have been reported.’
      • ‘While writing, I may choose a clear Quartz Crystal for clarity or a yellow Fluorite octahedron to help keep creative thoughts flowing.’
      • ‘Copper, Cu, has been found associated with cuprite octahedra at Pedra Preta, where these minerals occur on talc and magnesite.’
      • ‘Most of these specimens exhibit crystals that are cubic in habit; however, octahedra of both blue-gray and medium green have also been common.’
      • ‘A diamond crystal is essentially two pyramids stuck together - an octahedron.’
      • ‘There were smoky quartz crystals plus huge fluorite octahedra.’
      • ‘In contrast to crystals that resemble textbook drawings, the most frequently encountered gold crystals are skeletal octahedra.’


Late 16th century from Greek oktaedron, neuter (used as a noun) of oktaedros ‘eight-faced’.