| 1. | the lag in response exhibited by a body in reacting to changes in the forces, esp. magnetic forces, affecting it. Compare magnetic hysteresis. |
| 2. | the phenomenon exhibited by a system, often a ferromagnetic or imperfectly elastic material, in which the reaction of the system to changes is dependent upon its past reactions to change. |

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.
| hysteresis (hĭs'tə-rē'sĭs) Pronunciation Key
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. |