Merriam-Webster Collegiate Dictionary - hysteresis

 noun  (plural hystereses)  Etymology: New Latin, from Greek hysteresis shortcoming, from hysterein to be late, fall short, from hysteros later — more at out  Date: 1881 a retardation of an effect when the forces acting upon a body are changed (as if from viscosity or internal friction); especially a lagging in the values of resulting magnetization in a magnetic material (as iron) due to a changing magnetizing force  • hysteretic adjective