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 (geometry) a plane. This is just a linear equation where Conversely, it is easily shown that if and are constants and , and are not all zero, then the graph of the equation is a plane having the vector as a normal. This familiar equation for a plane is called the "general form" of the equation of the plane. Thus for example a regression equation of the form (with ) establishes a best-fit plane in three-dimensional space when there are two explanatory variables. Alternatively, a plane may be described parametrically as the set of all points of the form where "s"