hysteresis

Meanings

1. 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°.
2. Magnetic friction in dynamos, by which every reversal of magnetism in the iron causes dissipation of energy.

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.