Editing Dihedral angle (section)

==Geometry==
{{see also|Table of polyhedron dihedral angles}}

Every polyhedron has a dihedral angle at every edge describing the relationship of the two faces that share that edge. This dihedral angle, also called the ''face angle'', is measured as the [[internal angle]] with respect to the polyhedron. An angle of 0° means the face normal vectors are [[antiparallel vectors|antiparallel]] and the faces overlap each other, which implies that it is part of a [[Degeneracy (mathematics)|degenerate]] polyhedron. An angle of 180° means the faces are parallel, as in a [[List of uniform planar tilings|tiling]]. An angle greater than 180° exists on concave portions of a polyhedron.

Every dihedral angle in a polyhedron that is [[isotoxal figure|isotoxal]] and/or [[isohedral figure|isohedral]] has the same value. This includes the 5 [[Platonic solid]]s, the 13 [[Catalan solid]]s, the 4 [[Kepler–Poinsot polyhedron|Kepler–Poinsot polyhedra]], the 2 convex [[quasiregular polyhedron|quasiregular polyhedra]], and the 2 infinite families of [[bipyramid]]s and [[trapezohedron|trapezohedra]].