Dihedron

A dihedron is a polyhedron made of 2 faces which share all edges. It is degenerate if embedded in 3D Euclidean space, but it can be embedded in 2D spherical space. It can be thought of as a tiling of the sphere.

It is the three-dimensional case of a ditope.

Regular dihedra exist for all regular n-gons for n ≥ 2. The digonal dihedron, consisting of 2 digonal faces, is also the digonal hosohedron.