1. The rise and fall of the received signal at a mobile radio receiver due to the motion of the receiver through a region where the transmitted signal fluctuates rapidly. See also multipath.

2. Variations in signal strength at a receiver due to variations in the transmission medium. Destructive interference between two waves travelling by two different paths to the receiver is the most common cause of fading; this is termed interference fading.

Amplitude fading occurs when all transmitted frequencies are attenuated approximately equally, resulting in a smaller received signal. Selective fading occurs when some frequencies are more attenuated than others, resulting in a distorted received signal. Dellinger fade-out is a complete loss of the received signal, which may last for minutes or even hours following a burst of hydrogen particles from an eruption associated with a sunspot. This causes formation of a highly absorbent D-layer of the ionosphere lower than the regular E- and F-layers.