# entropy

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## entropy

[en´trŏ-pe]
1. in thermodynamics, a measure of the part of the internal energy of a system that is unavailable to do work. In any spontaneous process, such as the flow of heat from a hot region to a cold region, entropy always increases.
2. the tendency of a system to move toward randomness.
3. in information theory, the negative of information, a measure of the disorder or randomness in a physical system. The theory of statistical mechanics proves that this concept is equivalent to entropy as defined in thermodynamics.
4. diminished capacity for spontaneous change, as occurs in the psyche in aging.

## en·tro·py (S),

(en'trŏ-pē),
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, entropy is a measure of randomness or disorder. Entropy occurs in the Gibbs free energy (G) equation: ΔG = ΔH - TΔSH, change in enthalpy or heat content; T, absolute temperature; ΔS, change in entropy; ΔG, change in Gibbs free energy).
[G. entropia, a turning toward]

## entropy

/en·tro·py/ (en´tro-pe)
1. the measure of that part of the heat or energy of a system not available to perform work; it 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.

## entropy

[en′trəpē]
Etymology: Gk, en + tropos, a turning
the tendency of a system to change from a state of order to a state of disorder, expressed in physics as a measure of the part of the energy in a thermodynamic system that is not available to perform work. According to the principles of evolution, living organisms tend to go from a state of disorder to a state of order in their development and thus appear to reverse entropy. However, maintaining a living system requires the expenditure of energy, leaving less energy available for work, with the result that the entropy of the system and its surroundings increases.

## en·tro·py

(S) (en'trŏ-pē)
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, a measure of randomness or disorder.
[G. entropia, a turning toward]

## entropy

the amount of disorder or the degree of randomness of a system. For example, when a protein is denatured by heat (see DENATURATION), the molecule (which has a definite shape) uncoils and takes up a random shape, producing a large change in entropy.

## entropy (enˑ·tr·pē),

n the propensity of matter and energy in a closed system to degrade into an equilibrium of uniform inertness and disorder. The apparent suspension of entropy in animate systems is used to support the philosophy of vitalism.

## entropy

1. in thermodynamics, a measure of the part of the internal energy of a system that is unavailable to do work. In any spontaneous process, such as the flow of heat from a hot region to a cold region, entropy always increases.
2. in information theory, the negative of information, a measure of the disorder or randomness in a physical system. The theory of statistical mechanics proves that this concept is equivalent to entropy as defined in thermodynamics.
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