The difference in response with the independent variable increasing versus decreasing. Usually caused by friction in a mechanism. Relevant to the calibration testing of instruments, both analog and discrete.
For continuous measurement devices, the response of a sensor at some stimulus value (increasing) will not be the exactly the same as the response of that same sensor at that same value when decreasing.
For process switches, the “trip” the value at which a switch changes state when its stimulus increases is not the same value it changes state when its stimulus decreases.