Rotational symmetry, also known as radial symmetry, is represented by an axis about which the object rotates in its corresponding symmetry operation. A group of proper rotations is denoted as C n, where the degrees of rotation that restore the object is 360/n (C 2 = 180º rotation, C 3 = 120º rotation, C 4 = 90º rotation, C 5 = 72º rotation). The C n notation is also used for the related, more abstract, cyclic group.