Entropy

En"tro*py (?), n. [Gr. ? a turning in; ? in + ? a turn, fr. ? to turn.] (Thermodynamics) A certain property of a body, expressed as a measurable quantity, such that when there is no communication of heat the quantity remains constant, but when heat enters or leaves the body the quantity increases or diminishes. If a small amount, h, of heat enters the body when its temperature is t in the thermodynamic scale the entropy of the body is increased by h ? t. The entropy is regarded as measured from some standard temperature and pressure. Sometimes called the thermodynamic function.

The entropy of the universe tends towards a maximum.
Clausius.