The progressive reduction in aMPLitude of a signal as it travels farther from the point of origin. For exaMPLe, an electric signal' s aMPLitude reduces with distance due to electrical impedance. Attenuation is usually measured in decibels [per metre?]. Attenuation does not iMPLy appreciable modification of the shape of the waveform (distortion), though as the signal aMPLitude falls the signal-to-noise ratio will also fall unless the channel itself is noise free or the signal is aMPLified at some intermediate point(s) along the channel. ["Networking Essentials, second edition", Microsoft Corporation, pub. Microsoft Press 1997]. (2003-07-29)