# entropy

## noun

en·​tro·​py
plural entropies
1
thermodynamics : a measure of the unavailable energy in a closed thermodynamic system that is also usually considered to be a measure of the system's disorder, that is a property of the system's state, and that varies directly with any reversible change in heat in the system and inversely with the temperature of the system
broadly : the degree of disorder or uncertainty in a system
2
a
: the degradation of the matter and energy in the universe to an ultimate state of inert uniformity
Entropy is the general trend of the universe toward death and disorder. James R. Newman
b
: a process of degradation or running down or a trend to disorder
The deterioration of copy editing and proof-reading, incidentally, is a token of the cultural entropy that has overtaken us in the postwar years. John Simon
4
statistical mechanics : a factor or quantity that is a function of the physical state of a mechanical system and is equal to the logarithm of the probability for the occurrence of the particular molecular arrangement in that state
5
communication theory : a measure of the efficiency of a system (such as a code or a language) in transmitting information, being equal to the logarithm of the number of different messages that can be sent by selection from the same set of symbols and thus indicating the degree of initial uncertainty that can be resolved by any one message
entropic
en-ˈtrō-pik
-ˈträ-pik

## Did you know?

With its Greek prefix en-, meaning "within", and the trop- root here meaning "change", entropy basically means "change within (a closed system)". The closed system we usually think of when speaking of entropy (especially if we're not physicists) is the entire universe. But entropy applies to closed systems of any size. Entropy is seen when the ice in a glass of water in a warm room melts—that is, as the temperature of everything in the room evens out. In a slightly different type of entropy, a drop of food coloring in that glass of water soon spreads out evenly. However, when a nonphysicist uses the word, he or she is usually trying to describe a large-scale collapse.

## Example Sentences

Recent Examples on the Web Like thousands of tenant houses in Mississippi, it was being consumed by weather and entropy. David Brown, Smithsonian Magazine, 1 Dec. 2022 In a nutshell, this calculation of the entropy was a count of all the missing information that gets locked behind an event horizon. Paul Sutter, Ars Technica, 3 Oct. 2022 Naert plans to work with theorists to better understand what this type of temperature means, along with measuring and understanding the role of entropy in his device. Sophia Chen, WIRED, 14 Oct. 2022 Featureless equilibrium is the state of maximum entropy, toward which the Second Law drives us. Frank Wilczek, WSJ, 1 Sep. 2022 Contrast this with the entropy of a more traditional system—say, a gas in a box. Edgar Shaghoulian, Scientific American, 22 Aug. 2022 The first major clue came in the late 1990s when theoretical physicist Juan Maldacena calculated the entropy of a black hole. Paul Sutter, Ars Technica, 3 Oct. 2022 There’s clearly something going on linking area, entropy and information. Quanta Magazine, 20 Apr. 2022 Hawking's final paper revisited black hole entropy and the no-hair concept. Jennifer Ouellette, Ars Technica, 9 Sep. 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'entropy.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

## Word History

Etymology

International Scientific Vocabulary en- entry 2 + Greek tropē change, literally, turn, from trepein to turn

First Known Use

1867, in the meaning defined at sense 1

Time Traveler
The first known use of entropy was in 1867

entropy

## Cite this Entry

“Entropy.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/entropy. Accessed 1 Dec. 2022.

entropy

## noun

en·​tro·​py
plural entropies
: a measure of the unavailable energy in a closed thermodynamic system that is also usually 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 system

## More from Merriam-Webster on entropy

Last Updated: - Updated example sentences
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