POLYHEDRON

(Yunanca köken — orijinale bakınız.) In Geometry, a solid body bounded by many faces or planes. When all the faces are regular polygons, similar and equal to each other, the solid becomes a regular body. It may be demonstrated that only five regular solids can exist; namely, the tetraedron, the hexaedron, the octaedron, the dodecaedron, and the icosaedron. See the terms; see also Platonic Bodies. Polyhedron. In Optics. See Poly scope. POLY HYMN I A, the muse who presided over lyric poetry: — Nee Poljhymnia Lesboam refugit tendere barb it on. Horn. Od. i. 1, POLYMPGNITE. {Gr. ^oXv;, and fji,iymiJ.i, I mix.) A mineral which occurs in small prismatic crystals of a metallic lustre j its constituents are titanic acid, zirconia, lime, yttria, oxides of iron, cerium and manganese, magnesia, pota a, silica, and oxide of tin. It is found in Norway. POLYNOMIAL, or MULTINOMIAL, in Algebra, denotes a quantity having many terms. Such, for example, is the expre ion a-h26-l-3c + wrf, . [s. 970]