Any undesired change in the waveform of an electric signal passing through a circuit or other transmission medium.

In general, the extent to which a system fails to accurately reproduce the characteristics of an input signal at its output.

Any undesired change in the waveform of a sound wave.

A type of aberration in which there is variation in magnification with the distance from the axis of an optical system, so that images are not geometrically similar to their objects.