An icosahedron is a three-dimensional geometric shape that has twenty triangular faces, twelve vertices, and thirty edges. It is one of the five Platonic solids, which are regular, convex polyhedra with identical faces. The icosahedron is known for its symmetrical properties and is often used in various fields, including mathematics, art, and gaming. In nature, icosahedral shapes can be found in certain viruses, such as the adenovirus, which have an icosahedral symmetry. This shape allows for efficient packing of genetic material and proteins. The icosahedron also appears in dice used in tabletop role-playing games, where it is commonly referred to as a "d20."