ICOSAHEDRON (Gr. e'IKOVL, twenty, and Ebpa, a

See also:

• FACE (from Lat. fades, derived either from facere, to make, or from a root fa-, meaning " appear "; cf. Gr. cbatvstv)

face or

See also:

• BASE

base)  , in geometry, a solid enclosed by twenty faces . The " regular icosahedron " is one of the Platonic solids; the " great icosahedron " is a Kepler-Poinsot solid; and the " truncated icosahedron " is an Archimedean solid (see POLYHEDRON) . In crystallography the icosahedron is a possible form, but it has not been observed; it is closely simulated by a combination of the octahedron and pentagonal dodecahedron, which has twenty triangular faces, but only eight are equilateral, the remaining twelve being isosceles (see CRYSTALLOGRAPHY) .