This expression refers to the assumption, essential to conventional @T06470@, that the energy of the system may be expressed as the sum of components associated with different @D01572@. In transition-state theory it is assumed that the energy of the motion of the system through the @D01823@ of the @P04780@ is separable into various components. In many practical calculations it is assumed that the energy of the system is separable into electronic, vibrational, rotational and translational energy.