image In the literature the polar perturbations are also called even-parity because they are characterized by their behavior under parity operations as discussed earlier, and in the same way the axial perturbations are called odd-parity . We will stick to the polar/axial terminology since there is a confusion with the definition of the parity operation, the reason is that to most people, the words ``even'' and ``odd'' imply that a mode transforms under image as image or image respectively (for n some integer). However only the polar modes with even image have even parity and only axial modes with even image have odd parity. If image is odd, then polar modes have odd parity and axial modes have even parity. Another terminology is to call the polar perturbations spheroidal and the axial ones toroidal . This definition is coming from the study of stellar pulsations in Newtonian theory and represents the type of fluid motions that each type of perturbation induces. Since we are dealing both with stars and black holes we will stick to the polar/axial terminology.