Polyhedron

solid in three dimensions with flat faces
Some polyhedra
Dodecahedron light blue.svg
Dodecahedron
(Regular polyhedron)
Small stellated dodecahedron.png
Small stellated dodecahedron
(Regular star)
Icosidodecaëder.png
Icosidodecahedron
(Uniform)
Great cubicuboctahedron.png
Great cubicuboctahedron
(Uniform star)
Rhombictriacontahedron.jpg
Rhombic triacontahedron
(Uniform dual)
Elongated pentagonal cupola.png
Elongated pentagonal cupola
(Convex regular-faced)
Octagonal prism.png
Octagonal prism
(Uniform prism)
Square antiprism.png
Square antiprism
(Uniform antiprism)

A polyhedron (one polyhedron, many polyhedra, or polyhedrons) is a geometrical shape. It is a 3D shape with flat faces, and straight edges. Each face is a polygon surrounded by edges. Usually it is defined by the number of faces, or edges.

Most dice are polyhedra.

Two types of polyhedron are convex and concave. The line connecting any two points of a convex polyhedron is inside the polyhedron. The line connecting two points of a concave polyhedron may go outside the polyhedron.

Mathematicians do not agree on what makes a polyhedron. They do agree that there are five Platonic solids, which are regular polyhedra. On a regular polyhedron, all faces are the same and all vertices are the same.

NamingEdit

Usually, polyhedra are named by the number of faces they have. The first polyhedra are the tetrahedron, which is made of four triangles, pentahedron (five faces, can look like a four-sided pyramid), hexahedron (six faces, a cube if it is regular), heptahedron (seven faces) and octahedron (eight faces). Prisms, pyramids and other shapes can also be named according to how many faces they have.

Other websitesEdit