1.82: Point group
A point group is a group of symmetry operations all of which leave at least one point unmoved. A crystallographic point group is a point group that maps a point lattice onto itself: in three dimensions rotations and rotoinversions are restricted to 1, 2, 3, 4, 6 and \(\bar 1\) , \(\bar 2\) (= m ), \(\bar 3\) , \(\bar 4\) , \(\bar 6\) respectively.