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.