Safety deviation is a term used in functional safety. Safety deviation (formerly safety accuracy) is the change in output due to (internal) component failures not analyzed in a Failure Modes, Effects, & Diagnostic Analysis (FMEDA). Safety accuracy is an input to the FMEDA analyst to advise the level of analysis detail for critical analog components. The term is defined, some of its history is described, the reasoning for its existence is given, and its application is presented.