# Dihedron

As a dihedral [ the dər ː ] ( dihedral, Greek for Zweiflächner ) a regular polygon (triangle, rectangle, etc.) is referred to, has the front and back. In the series of polyhedra thus it is the simplest two-dimensional special case.

The term is used within the group theory as a dihedral group and in the description of two dihedral angles, which are called dihedral angle.

In crystallography as non-closed forms are known, which consist of two surfaces having a common edge. These forms are called Doma (Greek δῶμα "house" ) when the two surfaces by reflection, or sphenoid ( to Greek σφήν " wedge ") if they are convicted by a twofold rotation axis together. The Doma is the general surface shape ( and namesake ) of the monoclinic crystal class domatischen (m), the sphenoid of the monoclinic - sphenoidischen class (2).

Dihedral angle between two planes