polygonal dihedron

{{Infobox polyhedron | name =Set of regular n-gonal dihedra | image =Hexagonal dihedron.svg | caption =Example hexagonal dihedron on a sphere | type =regular polyhedron or spherical tiling | euler = | faces =2 n-gons | edges =n | vertices =n | vertex_config =n.n | schläfli ={n,2} | wythoff =2 n 2 | coxeter = | symmetry =Dnh, [2,n], (*22n), order 4n | rotsymmetry =Dn, [2,n]+, (22n), order 2n | surface_area = | volume = | angle = | dual =regular n-gonal hosohedron | properties = | vertex_figure = | net =}} A dihedron (pl. dihedra) is a type of polyhedron, made of two polygon faces which share the same set of n edges. In three-dimensional Euclidean space, it is degenerate if its faces are flat, while in three-dimensional spherical space, a dihedron with flat faces can be thought of as a lens, an example of which is the fundamental domain of a lens space L(p,q). Dihedra have also been called bihedra, flat polyhedra, or doubly covered polygons.

As a spherical tiling, a dihedron can exist as nondegenerate form, with two n-sided faces covering the sphere, each face being a hemisphere, and vertices on a great circle. It is regular if the vertices are equally spaced.