Hermann-Mauguin notation is used to represent the symmetry elements in point groups, 
plane groups and space groups.

Space groups can be defined by combining the point group identifier with the uppercase 
P, C, I, or F for primitive, side-centered, body-centered, or face-centered lattices. 

Translations within the lattice in the form of screw axes and glide planes are also 
noted, giving a complete crystallographic space group.


The screw axis is noted by a number, n, where the angle of rotation is 360/n. The 
degree of translation is then added as a subscript showing how far along the axis 
the translation is, as a portion of the parallel lattice vector.

   In crystallography, a screw axis is a symmetry operation describing how a combination 
   of rotation about an axis and a translation parallel to that axis leaves a crystal 
   unchanged.


   In crystallography, a glide plane is symmetry operation describing how a reflection 
   in a plane, followed by a translation parallel with that plane, may leave the crystal 
   unchanged.