DISTORTION, in radio, a term denoting change in wave form which takes place as a wave passes through a circuit or transmis sion medium. Wave form distortion may consist of : (1 ) The presence in an output wave of a circuit of components having frequencies not present in the original wave due to circuit elements having non-linear characteristics; (2) a change in the relative amplitude of the component frequencies of a wave due to variation in the transmission efficiency of the circuit or transmission path for different frequencies included in the range involved; (3) a change in the relative phases of the component frequencies. Two or more of these forms of distortion may be present simul taneously.