DRIFT

A comparatively long-term change in an attribute or value of a system or equipment operational parameter. ( 188 ) Note 1: The drift should be characterized, such as "diurnal frequency drift " and " output level drift." Note 2: Drift is usually undesirable and unidirectional, but may be bidirectional, cyclic, or of such long-term duration and low excursion rate as to be negligible.