Editing Crystal system (section)

=== Crystal system ===
A crystal system is a set of point groups in which the point groups themselves and their corresponding [[space group]]s are assigned to a lattice system. Of the 32 [[crystallographic point group]]s that exist in three dimensions, most are assigned to only one lattice system, in which case both the crystal and lattice systems have the same name. However, five point groups are assigned to two lattice systems, rhombohedral and hexagonal, because both exhibit threefold rotational symmetry. These point groups are assigned to the trigonal crystal system.