- That fraction of heat (energy) content not available for the performance of work, usually because (in a chemical reaction) it has been used to increase the random motion of the atoms or molecules in the system; thus, e. is a measure of randomness or disorder. E. occurs in the Gibbs free energy (G) equation : ΔG = ΔH − TΔS (ΔH, change in enthalpy or heat content; T, absolute temperature; ΔS, change in e.). SEE ALSO: second law of thermodynamics. [G. entropia, a turning toward]
* * *en·tro·py 'en-trə-pē n, pl -pies a measure of the unavailable energy in a closed thermodynamic system that is also usu. considered to be a measure of the system's disorder and that is a property of the system's state and is related to it in such a manner that a reversible change in heat in the system produces a change in the measure which varies directly with the heat change and inversely with the absolute temperature at which the change takes place broadly the degree of disorder or uncertainty in a systemen·tro·pic en-'trōp-ik, -'träp- adjen·tro·pi·cal·ly -i-k(ə-)lē adv
* * *en·tro·py (enґtro-pe) [Gr. entropē a turning inward] 1. the measure of that part of the heat or energy of a system which is not available to perform work; entropy increases in all natural (spontaneous and irreversible) processes. Symbol S. 2. the tendency of any system to move toward randomness or disorder. 3. diminished capacity for spontaneous change, as occurs in the psyche in aging.
Medical dictionary. 2011.