hysteresis

English Noun

Definition

A property of a system such that an output value is not a strict function of the corresponding input, but also incorporates some lag, delay, or history dependence, and in particular when the response for a decrease in the input variable is different from the response for an increase. For example, a thermostat with a nominal setpoint of 75° might switch the controlled heat source on when the temperature drops below 74°, and off when it rises above 76°.

Etymology

Coined by Sir James Alfred Ewing from Ancient Greek ὑστέρησις (hustérēsis, “shortcoming”), from ὑστερέω (husteréō, “I am late, fall short”), from ὕστερος (hústeros, “later”). By surface analysis, hyster- (“higher, outer, latter, next”) + -esis.