en·​tro·​py | \ ˈen-trə-pē \
plural entropies

Definition of entropy

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
2a : 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

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Other Words from entropy

entropic \ en-​ˈtrō-​pik , -​ˈträ-​pik \ adjective
entropically \ en-​ˈtrō-​pi-​k(ə-​)lē , -​ˈträ-​ \ adverb

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.

Examples of entropy in a Sentence

Recent Examples on the Web

If the atoms were not super-cooled, rearranging them would have little effect on the system's overall entropy. Jennifer Ouellette, Ars Technica, "Penn State scientists build quantum version of Maxwell’s demon," 12 Sep. 2018 The place had the slightest touch of Grey Gardens to it, though without the unapologetic embrace of entropy. James Mcauley, Town & Country, "The Tragic, Fascinating History of Santo Sospir," 13 Aug. 2018 Smithson was a big believer in entropy and its laws that energy is more easily lost then gained. Anne Slowey, Condé Nast Traveler, "Fear and Self-Loathing in the American Southwest," 25 July 2018 The underlying law of our universe is entropy, or constant descent into disorder. WSJ, "Modern Heraclitus: Trump’s Genius for Chaos," 1 July 2018 And the expansion, in turn, subjected #MeToo to the familiar physics of American political entropy. Megan Garber, The Atlantic, "Is #MeToo Too Big?," 4 July 2018 On his memorial stone is inscribed his equation, which describes the entropy of a black hole. Laura Yan, Popular Mechanics, "Stephen Hawking's Voice Got Beamed To a Black Hole," 17 June 2018 The stone is also inscribed with one of Hawking's equations describing the entropy of a black hole. NBC News, "Stephen Hawking's ashes buried in Westminster Abbey," 15 June 2018 His music, even since Pavement melted into entropy in 1999, has been jarring and opaque, defined by lyrics that circle around homonyms and puns, or break from generational observations into non sequiturs. Rob Tannenbaum, New York Times, "Stephen Malkmus Doesn’t Think He Was a Jerk," 14 May 2018

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.

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First Known Use of entropy

1868, in the meaning defined at sense 1

History and Etymology for entropy

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

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The first known use of entropy was in 1868

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en·​tro·​py | \ ˈen-trə-pē \
plural entropies

Medical Definition of entropy

: 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

Other Words from entropy

entropic \ en-​ˈtrōp-​ik , -​ˈträp-​ \ adjective
entropically \ -​i-​k(ə-​)lē \ adverb

More from Merriam-Webster on entropy

Britannica English: Translation of entropy for Arabic Speakers

Britannica.com: Encyclopedia article about entropy

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