Dihedral angle

In geometry, the angle between two planes is called their dihedral angle. It can defined as the angle between two lines normal to the planes.

The dihedral angle is a property of all polyhedra, regular and non-regular. More specifically, it is the property of pairs of faces: the dihedral angle is the angle at which two adjacent faces meet. Thus, the dihedral angle of a cube is 90°, while the dihedral angle of a dodecahedron is 116° 34′.