(n) :
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?