The crystallographic point groups in two dimensions will involve only symmetry axes of order 1, 2, 3, 4, 6 . On comparing with three dimensional point groups:

a) axes are not needed. For example the user can verify that in two dimensions

     and    

b) the reflection with respect to a plane is substituted by a reflection with respect to a line (with the same symbol m).

The total number of point groups in the plane is 10; they are indicated by the symbols: