The polarization of an antenna in a given direction is defined in one of two ways. If the antenna is being excited and is radiating, its polarization is defined to be the polarization of the radiated wave. If the antenna is receiving energy, its polarization is said to be the polarization of an incident wave from the given direction that results in maximum available power at the antenna terminals. If a direction is not stated, the polarization is taken to be the polarization in the direction of maximum gain.