Dihedral Group - Notation

Notation

There are two competing notations for the dihedral group associated to a polygon with n sides. In geometry the group is denoted D_n, while in algebra the same group is denoted by D_2n to indicate the number of elements. Coxeter notation is another notation, denoting the reflectional dihedral symmetry as, order 2n, and rotational dihedral symmetry as +, order n. Orbifold notation gives the reflective symmetry as *nn and rotational symmetry as n.

In this article, D_n (and sometimes Dih_n) refers to the symmetries of a regular polygon with n sides.