Polar point group

In geometry, a polar point group is a point group in which there is more than one point that every symmetry operation leaves unmoved. The unmoved points will constitute a line, a plane, or all of space. In geometry, a polar point group is a point group in which there is more than one point that every symmetry operation leaves unmoved. The unmoved points will constitute a line, a plane, or all of space. A straight line joining two unmoved points defines a unique axis of rotation, called a polar direction, unless the symmetry operations do not allow any rotation at all, such as mirror symmetry, in which case the polar direction must be parallel to any mirror planes.