entropy
Pluralentropies (some meanings)
- 1The tendency of a system, when left to itself, to break down into chaos.
Left without maintenance, the abandoned rail line surrendered to entropy within a decade.
Every organization fights entropy; without steady attention, its procedures drift into disarray.
UsageOften treated as an opponent: people fight entropy, surrender to entropy, or say entropy wins.
Similardecay, disorder, chaos, deterioration
Oppositeorder
Note
Everyday speech borrows the rule behind the thermodynamic measure (in an isolated system, entropy never decreases) and applies it to houses, gardens and institutions: whatever is left alone runs down.
Checked 2 Nov 2026 · 1 fact
- The second law of thermodynamics states that entropy never decreases in an isolated system. farside.ph.utexas.edu
- 2In thermodynamics, a quantity measuring the disorder of a system, or how far its energy has spread out and is unavailable for doing useful work.
Mixing two gases raises the total entropy, because the mixed state can be realized by vastly more microstates than the separated one.
Statistical physicists calculate the entropy of a crystal by counting the microstates consistent with its measured energy.
Note
Here entropy comes from counting: Boltzmann's formula, S = k ln W, multiplies Boltzmann's constant by the natural logarithm of W, the number of microstates. A microstate is one exact specification of every particle, its position and its momentum; a macrostate is what can be measured, such as temperature or pressure. Disorder in this sense means that the measurable state can arise in a great many ways.
- 3In information theory, the average amount of information, or uncertainty, in each symbol or message a source produces, usually measured in bits.
Shannon defined the entropy of a source as the average information carried by each symbol it emits.
Password strength is often estimated from the entropy of the process that generated the password.
Note
Information theory uses the word for average surprise, usually measured in bits, and often calls it Shannon entropy. A source whose next symbol can always be predicted has none; for a fixed symbol set, one whose symbols are independent and equally likely has the most. That is why random data resists compression while ordinary text, full of patterns, shrinks easily.
Checked 31 Oct 2026 · 6 facts
- Information entropy measures average surprise and can be measured in bits. en.wikipedia.org
- Information entropy is also called Shannon entropy. en.wikipedia.org
- A completely predictable source has zero entropy. courses.physics.illinois.edu
- For a fixed alphabet, maximum entropy per symbol requires independent, equally likely symbols. Equal marginal probabilities alone are insufficient: dependencies can make subsequent symbols predictable. people.math.harvard.edu
- Random data resists compression because its entropy is high. people.math.harvard.edu
- Patterns in ordinary text allow substantial compression. web.stanford.edu
Practice
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Origin
Attested in English by 1866, as a translation of German Entropie, coined in 1865 by Rudolph Clausius on the model of Energie (“energy”), replacing the root of Ancient Greek érgon (“work”) with Ancient Greek tropḗ (“transformation”).
Checked 31 Oct 2026 · 5 facts
- English use is documented by July 1866, in Clausius's article in Philosophical Magazine, volume 32, pages 1–17. Thus 1867 is too late. kennethcaneva.com
- English entropy translates German Entropie. en.wiktionary.org
- Clausius coined the German term in 1865. en.wiktionary.org
- Clausius deliberately modeled the name on energy. webserver.lemoyne.edu
- The formation substitutes Greek tropḗ, meaning transformation, for the root érgon, meaning work. en.wiktionary.org