Noise figure

From Glossary of Meteorology

noise figure

(Or noise factor.) A number by which the performance of a radio receiver can be specified.

Essentially, the noise figure is the ratio of the noise generated by the actual receiver to the noise output of an "ideal" receiver with the same overall gain and bandwidth when the receivers are connected to a room temperature load. The noise power from a simple load is equal to kTB, where k is Boltzmann's constant; T the absolute temperature of the load, for example, resistor; and B the measurement bandwidth.
See also noise level, signal-to-noise ratio.