# Effective area or effective aperture of antenna

The effective area simply represents how much power is captured from the plane wave and delivered by the antenna. The explanation begins oft with assumption that antennas have the same polarization.

A plane wave with the same polarization as the receive antenna is incident upon the antenna. Further assume that the wave is travelling towards the antenna in the antenna's direction of maximum radiation (the direction from which the most power would be received).

Polarization is the orientation in field, so can I conclude that antennas that have the different polarization the effective area are equal zero? And why effective aperture of an antenna is a parameter defined for the receiving antenna?