Definition of entropy Entropy

/ɛˈntɹʌpi/ - [entrupee] - en•tro•py

We found 15 definitions of entropy from 7 different sources.

What does entropy mean?

WordNet

Noun
entropy - (thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; "entropy increases as matter and energy in the universe degrade to an ultimate state of inert uniformity"
		randomness, S
		physical property any property used to characterize matter and energy and their interactions
		thermodynamics the branch of physics concerned with the conversion of different forms of energy
entropy - (communication theory) a numerical measure of the uncertainty of an outcome; "the signal contained thousands of bits of information"
		information, selective information
		information measure a system of measurement of information based on the probabilities of the events that convey information

= synonym
= antonym
= related word

Wiktionary

entropy (Noun)
Strictly thermodynamic entropy. A measure of the amount of energy in a physical system that cannot be used to do work.
entropy (Noun)
The thermodynamic free energy is the amount of work that a thermodynamic system can perform; it is the internal energy of a system minus the amount of energy that cannot be used to perform work. That unusable energy is given by the entropy of a system multiplied by the temperature of the system. Note that, for both Gibbs and Helmholtz free energies, temperature is assumed to be fixed, so entropy is effectively directly proportional to useless energy.
entropy (Noun)
A measure of the disorder present in a system.
entropy (Noun)
Ludwig Boltzmann defined entropy as being directly proportional to the natural logarithm of the number of microstates yielding an equivalent thermodynamic macrostate with the eponymous constant of proportionality. Assuming by the fundamental postulate of statistical mechanics, that all microstates are equally probable, this means, on the one hand, that macrostates with higher entropy are more probable, and on the other hand, that for such macrostates, the quantity of information required to describe a particular one of its microstates will be higher. That is, the Shannon entropy of a macrostate would be directly proportional to the logarithm of the number of equivalent microstates making it up. In other words, thermodynamic and informational entropies are rather compatible, which shouldn't be surprising since Claude Shannon derived the notation 'H' for information entropy from Boltzmann's H-theorem.
entropy (Noun)
The capacity factor for thermal energy that is hidden with respect to temperature.
entropy (Noun)
The dispersal of energy; how much energy is spread out in a process, or how widely spread out it becomes, at a specific temperature.
entropy (Noun)
A measure of the amount of information and noise present in a signal. Originally a tongue-in-cheek coinage, has fallen into disuse to avoid confusion with thermodynamic entropy.
entropy (Noun)
The tendency of a system that is left to itself to descend into chaos.

Webster DictionaryWebster's Unabridged Dictionary 📘

entropy (n.)
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.

Chambers DictionaryChamber's 20th Century Dictionary 📕

entropy
en′trop-i, n. a term in physics signifying 'the available energy.'

Electrical DictionaryThe Standard Electrical Dictionary 💡

entropy
Non-available energy. As energy may in some way or other be generally reduced to heat, it will be found that the equalizing of temperature, actual and potential, in a system, while it leaves the total energy unchanged, makes it all unavailable, because all work represents a fall in degree of energy or a fall in temperature. But in a system such as described no such fall could occur, therefore no work could be done. The universe is obviously tending in that direction. On the earth the exhaustion of coal is in the direction of degradation of its high potential energy, so that the entropy of the universe tends to zero. (See Energy, Degradation of.)
ENERGY tends to zero.]

Wikipedia

Entropy is the name of some different things.

The word Entropy came from the study of heat and energy in the period 1850 to 1900. Some very useful mathematical ideas about probability calculations emerged from the study of entropy. These ideas are now used in Information theory, Chemistry and other areas of study.