Hysteresis is a property of systems (usually physical systems) that do not instantly react to the forces applied to them, but react slowly, or do not return completely to their original state. The state of such a system depends on its immediate history. For example, if you push on a piece of putty it will assume a new shape, and when you remove your hand it will not return to its original shape, or at least not immediately and not entirely. The term derives from an ancient Greek word υστέρησις, meaning 'deficiency'. The term was coined by Sir James Alfred Ewing.