Point groups in three dimensions the finite subgroups of SO(3), are: the cyclic groups "C" (the rotation group of a canonical pyramid), the dihedral groups "D" (the rotation group of a uniform prism, or canonical bipyramid), and the rotation groups "T", "O" and "I" of a regular tetrahedron, octahedron/cube and icosahedron/dodecahedron. In particular, the dihedral groups "D", "D" etc. are the rotation groups of plane regular polygons embedded in three-dimensional space, and such a figure may be considered as a degenerate regular prism. Therefore, it is also called a "dihedron" (Greek: solid with two faces), which explains the name "dihedral group". The rotation group of
Plane of rotation everything in that plane it kept in the plane by the rotation. This could be described by a matrix like the following, with the rotation being through an angle (about the axis or in the plane): Another example is the Earth's rotation. The axis of rotation is the line joining the North Pole and South Pole and the plane of rotation is the plane through the equator between the Northern and Southern Hemispheres. Other examples include mechanical devices like a gyroscope or flywheel which store rotational energy in mass usually along the plane of rotation. In any three dimensional rotation