[ en-truh-pee ]
/ ˈɛn trə pi /
Save This Word!

  1. (on a macroscopic scale) a function of thermodynamic variables, as temperature, pressure, or composition, and differing from energy in that energy is the ability to do work and entropy is a measure of how much energy is not available. The less work that is produced, the greater the entropy, so when a closed system is void of energy, the result is maximum entropy.
  2. (in statistical mechanics) a measure of the randomness of the microscopic constituents of a thermodynamic system. Symbol: S
(in data transmission and information theory) a measure of the loss of information in a transmitted signal or message.
(in cosmology) a hypothetical tendency for the universe to attain a state of maximum homogeneity in which all matter is at a uniform temperature (heat death ).
a state of disorder, or a tendency toward such a state; chaos.
a doctrine of inevitable social decline and degeneration.
Smoothly step over to these common grammar mistakes that trip many people up. Good luck!
Question 1 of 7
Fill in the blank: I can’t figure out _____ gave me this gift.

Origin of entropy

First recorded in 1865; from German Entropie; from en-2 + trop(o)- + -y1


en·tro·pic [en-troh-pik, -trop-ik], /ɛnˈtroʊ pɪk, -ˈtrɒp ɪk/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What is entropy?

Entropy is a measure of the amount of energy that is unavailable to do work in a closed system.

In science, entropy is used to determine the amount of disorder in a closed system. We have a closed system if no energy from an outside source can enter the system.

For example, an ice cube is orderly because all of its energy (heat) is tightly packed together. As the ice melts, its energy spreads out, creating disorder. The ice cube’s entropy is increasing as the ice melts into the more disorderly state of a liquid (in this case, water).

In everyday use, entropy is used more broadly to refer to a lack of pattern or an increasing disorder, as in The coach’s disorganization spread throughout the team, creating some serious entropy at soccer practice.

Example: My clean room quickly fell into entropy after my younger brother and sister had a chaotic pillow fight in it.

Where does entropy come from?

The first records of entropy come from around 1865. It comes from the German entropie, which combines the prefix en-, meaning “within or in,” and the combining form -trope, meaning “one turned toward.”

Entropy is a measure of an increasingly complex situation that is happening within a system. Unless you study thermodynamics, you are most likely to notice an increase of entropy by what happens because of it, such as a tire deflating or ice cream melting.

You’re more likely to come across the broader, unscientific use of entropy as a synonym for “increased disorder” or “a collapse.”

Did you know ... ?

What are some other forms related to entropy?

  • entropic (adjective)
  • entropically (adverb)

What are some synonyms for entropy?

What are some words that share a root or word element with entropy

What are some words that often get used in discussing entropy?

How is entropy used in real life?

Although entropy has a narrow scientific meaning, its broader meaning is more commonly used.

Try using entropy!

In everyday speech, which of the following words is a synonym of entropy?

A. happiness
B. decline
C. organization
D. improvement

How to use entropy in a sentence

British Dictionary definitions for entropy

/ (ˈɛntrəpɪ) /

noun plural -pies
a thermodynamic quantity that changes in a reversible process by an amount equal to the heat absorbed or emitted divided by the thermodynamic temperature. It is measured in joules per kelvinSymbol: S See also law of thermodynamics
a statistical measure of the disorder of a closed system expressed by S = k log P + c where P is the probability that a particular state of the system exists, k is the Boltzmann constant, and c is another constant
lack of pattern or organization; disorder
a measure of the efficiency of a system, such as a code or language, in transmitting information

Word Origin for entropy

C19: from en- ² + -trope
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for entropy

[ ĕntrə-pē ]

A measure of the amount of energy in a physical system not available to do work. As a physical system becomes more disordered, and its energy becomes more evenly distributed, that energy becomes less able to do work. For example, a car rolling along a road has kinetic energy that could do work (by carrying or colliding with something, for example); as friction slows it down and its energy is distributed to its surroundings as heat, it loses this ability. The amount of entropy is often thought of as the amount of disorder in a system. See also heat death.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for entropy

[ (en-truh-pee) ]

A measure of the disorder of any system, or of the unavailability of its heat energy for work. One way of stating the second law of thermodynamics — the principle that heat will not flow from a cold to a hot object spontaneously — is to say that the entropy of an isolated system can, at best, remain the same and will increase for most systems. Thus, the overall disorder of an isolated system must increase.

notes for entropy

Entropy is often used loosely to refer to the breakdown or disorganization of any system: “The committee meeting did nothing but increase the entropy.”

notes for entropy

In the nineteenth century, a popular scientific notion suggested that entropy was gradually increasing, and therefore the universe was running down and eventually all motion would cease. When people realized that this would not happen for billions of years, if it happened at all, concern about this notion generally disappeared.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.