Glide operations combine mirroring with translation. The operation involves choosing a translation vector →U of the object and acts by mirroring through a plane parallel to vector, of →U. The plane through which the mirror part of the glide operation occurs is called a glide plane. The unit cell is almost al- ways chosen so that the glide plane is per- pendicular to a unit cell edge.
In crystals, screw rotations and/or glide reflections are additionally possible. These are rotations or reflections together with partial translation. These operations may change based on the dimensions of the crystal lattice.
The Bravais lattices may be considered as representing translational symmetry operations. Combinations of operations of the crystallographic point groups with the addition symmetry operations produce the 230 crystallographic space groups.