what is antenna gain?

what is antenna gain? the power through an antenna is bigger?
if the transmiter power is 0dbm and the antenna gain is 2dbi ,if no other loss ,the receiver power is 2dbm?

The antenna gain is the power out the transmission line from the antenna compared to the power with another antenna. The two basic comparison antennas are a dipole and a fictitious "isotropic" antenna which exists only in the world of mathematics and physics theories.

As a supplement, from what I know, the unit for Gain when we have a comparison between proposed antenna and dipole antenna is "dBd" or "dBi" in the case of isotropic antenna.
So,
It's not correct from my opinion.

regards!

As a supplement, from what I know, the unit for Gain when we have a comparison between proposed antenna and dipole antenna is "dBd" or "dBi" in the case of isotropic antenna.
So,
It's not correct from my opinion.

regards!