In general, electric (charge) radiation or magnetic (current, magnetic moment) radiation can be classified into multipoles E λ (electric) or M λ (magnetic) of order 2, e.g., E1 for electric dipole, E2 for quadrupole, or E3 for octupole. In transitions where the change in angular momentum between the initial and final states makes several multipole radiations possible, usually the lowest-order multipoles are overwhelmingly more likely, and dominate the transition.