Why is the ninth month called September?
1805, from Greek hysteresis "a coming short, a deficiency."
hysteresis hys·ter·e·sis (hĭs'tə-rē'sĭs)
n. pl. hys·ter·e·ses (-sēz)
The lagging of an effect behind its cause, as when the change in magnetism of a body lags behind changes in the magnetic field.
The dependence of the state of a system on the history of its state. For example, the magnetization of a material such as iron depends not only on the magnetic field it is exposed to but on previous exposures to magnetic fields. This "memory" of previous exposure to magnetism is the working principle in audio tape and hard disk devices. Deformations in the shape of substances that last after the deforming force has been removed, as well as phenomena such as supercooling, are examples of hysteresis.