Hysteresis

Hysteresis is a concept in physical science.
In hysteresis the output of a system depends not only on its input, but also on its history of past inputs. This is because the history affects the value of an internal state. To predict the future outputs of a system, either its internal state or its history must be known.
The effect may happen because of a lag between input and output. This effect disappears as the input changes more slowly. This effect meets the description of hysteresis given above, but is often referred to as "rate-dependent hysteresis" to distinguish it from hysteresis with a more durable memory effect.
Hysteresis occurs in ferromagnetic materials and ferroelectric materials. It also occurs in the deformation of some materials (such as rubber bands and shape-memory alloys). Many artificial systems are designed to have hysteresis: for example, in thermostats and computers.