| 释义 |
octahedron, octo-|ɒktəˈhiːdrən, -ˈhɛdrən|
Pl. -ons or -a. Also 6–8 octa(h)edrum, 6–9 octaedron, 7–9 octoedron.
[a. Gr. ὀκτάεδρον an octahedron, neuter of ὀκτάεδρος adj., eight-sided, f. ὀκτα- octa- + ἕδρα seat. In L. octaëdron, med.L. octa(h)edrum (Du Cange), F. octaèdre, also octohèdre (1587 in Hatz.-Darm.).]
Geom. A solid figure contained by eight plane faces; usually, one contained by eight triangles (such as is formed by two pyramids on opposite sides of a quadrilateral base); spec. the regular octahedron, one of the five regular solids, contained by eight equal equilateral triangles (formed by two equal pyramids with equilateral faces on a square base). Hence gen. any material body, esp. a crystal, of this form.
truncated octahedron, a fourteen-sided solid formed from the regular octahedron by truncating its six corners, and thus forming six new square faces, while cutting down the eight original triangular faces into regular hexagons.
1570Billingsley Euclid xiii. xiv. 406 An octohedron is deuided into two equall and like Pyramids. 1655H. More Antid. Ath. App. (1712) 183 There are Fiue regular Bodies..the Cube, the Tetraedrum, the Octaedrum, the Dodecaedrum, and the Eicosaedrum. 1656Stanley Hist. Philos. v. (1701) 186/2 The Octaedrons consist of eight like sides. 1823H. J. Brooke Introd. Crystallogr. 141 Octahedrons with rhombic bases. 1851Richardson Geol. v. 76 If we take a cube and cut off all the eight corners till the original faces disappear, we shall make it an octohedron. 1880E. Cleminshaw tr. Wurtz' Atom. Th. 142 The nitrates of barium, strontium, and lead,..crystallise in octohedra. |