Entropy is a fundamental scientific concept that quantifies the statistical probability of a system's state. It is a universal measure of multiplicity.

Entropy may also refer to:

• Entropy (classical thermodynamics), thermodynamic entropy in macroscopic terms, with less emphasis on the statistical explanation
• Entropy (statistical thermodynamics), the statistical explanation of thermodynamic entropy based on probability theory
  • Configuration entropy, the entropy change due to a change in the knowledge of the position of particles, rather than their momentum
  • Conformational entropy, the entropy change due to a change in the "configuration" of a particle (e.g. a right-handed vs. a left-handed polyatomic molecule)
• Tsallis entropy, a generalization of Boltzmann-Gibbs entropy
• von Neumann entropy, entropy in quantum statistical physics and quantum information science
• Entropy (order and disorder), the relationship of disorder with heat and work
• Entropy in thermodynamics and information theory, the relationship between thermodynamic entropy and information (Shannon) entropy
• Entropy (energy dispersal), dispersal of energy as a descriptor of entropy
• Entropy (astrophysics), the adiabatic constant

• Entropy (information theory), also called Shannon entropy, a measure of the unpredictability or information content of a message source
• Differential entropy, a generalization of Entropy (information theory) to continuous random variables
  • Entropy of entanglement, related to the Shannon and von Neumann entropies for entangled systems; reflecting the degree of entanglement of subsystems
• Algorithmic entropy an (incomputable) measure of the information content of a particular message
• Rényi entropy, a family of diversity measures generalising Shannon entropy; used to define fractal dimensions
• Topological entropy, a measure of exponential growth in dynamical systems; equivalent to the rate of increase of α->0 Renyi entropy of a trajectory in trajectory-space
• Volume entropy, a Riemannian invariant measuring the exponential rate of volume growth of a Riemannian metric
• Graph entropy, a measure of the information rate achievable by communicating symbols over a channel in which certain pairs of values may be confused

• Entropy encoding, data compression strategies to produce a code length equal to the entropy of a message
• Entropy (computing), an indicator of the number of random bits available to seed cryptography systems
• Entropy (anesthesiology), a measure of a patient's cortical function, based on the mathematical entropy of EEG signals
• Entropy (ecology), measures of biodiversity in the study of biological ecology, based on Shannon and Rényi entropies
• Social entropy, a measure of the natural decay within a social system

• Entropy (film), a 1999 film by Phil Joanou
• "Entropy" (Buffy episode), 2002
• "Entropy", an episode of Criminal Minds season 11

• Entropy (board game)
• Entropy (video game)
• Entropy or Alchemiss, a character in Freedom Force vs the 3rd Reich
• N. Tropy, a character from Crash Bandicoot: Warped
• Entropy: Zero, a Source mod for Half-Life 2 released in 2017 developed by Breadman
• Entropy: Zero 2, a sequel to Entropy: Zero released in 2022
• Entropy: Zero - Uprising, a mod of Entropy: Zero developed by Employee8 and Filipad

• Entropy: A New World View, a book by Jeremy Rifkin and Ted Howard
• "Entropy", a 1960 short story by Thomas Pynchon
• "Entropy", a 1995 short story by Leanne Frahm
• Entropy (journal), a scientific journal published by MDPI
• Entropy (magazine), an online literary magazine

• Entropy, a 2005 album by Anathallo and Javelins
• Entropy / Send Them, an EP by DJ Shadow and the Groove Robbers
• "Entropy", a song by Bad Religion from Against the Grain
• "Entropy", a song by Kelly Osbourne from Sleeping in the Nothing
• "Entropy", a song by VNV Nation from Matter + Form
• "Entropy", a song by Moxy Früvous from The 'b' Album
• "Entropy", a song by Brymo from Oṣó
• "Entropy", a song by Daniel Caesar from Case Study 01
• "Entropy", a song by Beach Bunny from Emotional Creature
• "Entropy", a song by MC Hawking
• "Entropy", a song by Grimes and Bleachers
• Entropia (album), an album by Pain of Salvation
• Entropy, a track by Nigel Stanford
• The Book Of Us: Entropy, an album by DAY6

• Entropy (choreography), the difference between a transcription and a performance

• Entropy (package manager), a Sabayon Linux utility
• Exluna Entropy, computer graphics rendering software
• Information entropy, relating to disruptive actions taken in Internet vigilantism

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