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.