A regular dihedron, {"n", 2} (2-hedron) in three-dimensional Euclidean space can be considered a degenerate prism consisting of two (planar) "n"-sided polygons connected "back-to-back", so that the resulting object has no depth, analogously to how a digon can be constructed with two line segments. However, 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 around a great circle. It is "regular" if the vertices are equally spaced.