A polyhedron having twenty triangular faces.The faces of a regular icosahedron are all equilateral triangles.The see thumbnail to rightregular icosahedron is one of the five Platonic solids (along with the tetrahedron, hexahedron (cube), octahedron, and the dodecahedron).The icosahedron vacuus was drawn by Leonardo da Vinci (Italian,1452-1519) for the "De divina proportione" treaty by Luca Pacioli, in which the Renaissance artist and the mathematician define rules determining what is beautiful.The plural can be either icosahedrons or icosahedra.Examples: Fra Giovanni da Verona (Italian), three panels of wood intarsia, 1520: Each conveys the appearance of open cupboard doors ? a trompe l'oeil effect resulting from the use of linear perspective. The first panel: a Campanus sphere, a mazzocchio, and various instruments of the geometer. The second panel: a complex polyhedron which can be constructed by erecting a pyramid of equilateral triangles on each face of an icosidodecahedron. The third: the Campanus sphere again, along with an icosahedron and a truncated icosahedron.Other resources about cubes: Low-tech models of polyhedra. Here are printable templates for making paper models of the regular polyhdra including one for a icosahedron in two sections, one for its top, and one for its bottom. To use the templates, print the images, and then copy them onto heavy card stock (60 lb. stock is best) with as much magnification as seems suitable.Also see mathematics, polygon, and vertex.