13 results for: entropy

Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This

en·tro·py

Audio Help [en-truh-pee] Pronunciation Key

–noun

Thermodynamics.

a.	(on a macroscopic scale) a function of thermodynamic variables, as temperature, pressure, or composition, that is a measure of the energy that is not available for work during a thermodynamic process. A closed system evolves toward a state of maximum entropy.

b.	(in statistical mechanics) a measure of the randomness of the microscopic constituents of a thermodynamic system. Symbol: S

2.	(in data transmission and information theory) a measure of the loss of information in a transmitted signal or message.

3.	(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).

4.	a doctrine of inevitable social decline and degeneration.

[Origin: < G Entropie (1865); see en-², -tropy

]

—Related forms

en·tro·pic

Audio Help [en-troh-pik, -trop-ik] Pronunciation Key, adjective

en·tro·pi·cal·ly, adverb

Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.

Encyclopædia Britannica, Inc.
entropy

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American Heritage Dictionary - Cite This Source - Share This

en·tro·py Audio Help (ěn'trə-pē) Pronunciation Key
n. pl. en·tro·pies

Symbol S For a closed thermodynamic system, a quantitative measure of the amount of thermal energy not available to do work.
A measure of the disorder or randomness in a closed system.
A measure of the loss of information in a transmitted message.
The tendency for all matter and energy in the universe to evolve toward a state of inert uniformity.
Inevitable and steady deterioration of a system or society.

[German Entropie : Greek en-, in; see en-² + Greek tropē, transformation; see trep- in Indo-European roots.]

en·tro'pic (ěn-trō'pĭk, -trŏp'ĭk) adj., en·tro'pi·cal·ly adv.

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The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

Online Etymology Dictionary - Cite This Source - Share This
entropy

1868, from Ger. Entropie "measure of the disorder of a system," coined 1865 (on analogy of Ger. Energie) by physicist Rudolph Clausius (1822-1888) from Gk. entropia "a turning toward," from en- "in" + trope "a turning" (see trope).

WordNet - Cite This Source - Share This

entropy
noun
1.	(communication theory) a numerical measure of the uncertainty of an outcome; "the signal contained thousands of bits of information" [syn: information]
2.	(thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; "entropy increases as matter and energy in the universe degrade to an ultimate state of inert uniformity" [syn: randomness]

The American Heritage Science Dictionary - Cite This Source - Share This

entropy Audio Help (ěn'trə-pē) Pronunciation Key
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 © 2002 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

American Heritage New Dictionary of Cultural Literacy, Third Edition - Cite This Source - Share This
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.

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

Note: 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.

[Chapter:] Physical Sciences and Mathematics

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

American Heritage Stedman's Medical Dictionary - Cite This Source - Share This

en·tro·py (ntr-p)
n.

For a closed thermodynamic system, a quantitative measure of the amount of thermal energy not available to do work.
A measure of the disorder or randomness in a closed system.

en·tropic (

n-tr

k, -tr

k) adj.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Merriam-Webster's Medical Dictionary - Cite This Source - Share This

Main Entry: en·tro·py
Pronunciation: 'en-tr&-pE
Function: noun
Inflected Form: plural -pies
: 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 —en·tro·pic /en-'trOp-ik, -'träp-/ adjective —en·tro·pi·cal·ly /-i-k(&-)lE/ adverb

Free On-line Dictionary of Computing - Cite This Source - Share This

entropy theory
A measure of the disorder of a system. Systems tend to go from a state of order (low entropy) to a state of maximum disorder (high entropy).
The entropy of a system is related to the amount of information it contains. A highly ordered system can be described using fewer bits of information than a disordered one. For example, a string containing one million "0"s can be described using run-length encoding as [("0", 1000000)] whereas a string of random symbols (e.g. bits, or characters) will be much harder, if not impossible, to compress in this way.
Shannon's formula gives the entropy H(M) of a message M in bits:
H(M) = -log2 p(M)
Where p(M) is the probability of message M.
(1998-11-23)

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

Entropy

En*tro"pi*um\, n. [NL. See Entropy.] (Med.) The inversion or turning in of the border of the eyelids.

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

Entropy

En"tro*py\, n. [Gr. ? a turning in; ? in + ? a turn, fr. ? to turn.] (Thermodynamics) A certain property of a body, expressed as a measurable quantity, such that when there is no communication of heat the quantity remains constant, but when heat enters or leaves the body the quantity increases or diminishes. If a small amount, h, of heat enters the body when its temperature is t in the thermodynamic scale the entropy of the body is increased by h ? t. The entropy is regarded as measured from some standard temperature and pressure. Sometimes called the thermodynamic function.

The entropy of the universe tends towards a maximum. --Clausius.

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

entropy

Heat\, n. [OE. hete, h[ae]te, AS. h?tu, h?to, fr. h[=a]t hot; akin to OHG. heizi heat, Dan. hede, Sw. hetta. See Hot.]

1. A force in nature which is recognized in various effects, but especially in the phenomena of fusion and evaporation, and which, as manifested in fire, the sun's rays, mechanical action, chemical combination, etc., becomes directly known to us through the sense of feeling. In its nature heat is a mode if motion, being in general a form of molecular disturbance or vibration. It was formerly supposed to be a subtile, imponderable fluid, to which was given the name caloric.

Note: As affecting the human body, heat produces different sensations, which are called by different names, as heat or sensible heat, warmth, cold, etc., according to its degree or amount relatively to the normal temperature of the body.

2. The sensation caused by the force or influence of heat when excessive, or above that which is normal to the human body; the bodily feeling experienced on exposure to fire, the sun's rays, etc.; the reverse of cold.

3. High temperature, as distinguished from low temperature, or cold; as, the heat of summer and the cold of winter; heat of the skin or body in fever, etc.

Else how had the world . . . Avoided pinching cold and scorching heat! --Milton.

4. Indication of high temperature; appearance, condition, or color of a body, as indicating its temperature; redness; high color; flush; degree of temperature to which something is heated, as indicated by appearance, condition, or otherwise.

It has raised . . . heats in their faces. --Addison.

The heats smiths take of their iron are a blood-red heat, a white-flame heat, and a sparking or welding heat. --Moxon.

5. A single complete operation of heating, as at a forge or in a furnace; as, to make a horseshoe in a certain number of heats.

6. A violent action unintermitted; a single effort; a single course in a race that consists of two or more courses; as, he won two heats out of three.

Many causes . . . for refreshment betwixt the heats. --Dryden.

[He] struck off at one heat the matchless tale of "Tam o'Shanter." --J. C. Shairp.

7. Utmost violence; rage; vehemence; as, the heat of battle or party. "The heat of their division." --Shak.

8. Agitation of mind; inflammation or excitement; exasperation. "The head and hurry of his rage." --South.

9. Animation, as in discourse; ardor; fervency.

With all the strength and heat of eloquence. --Addison.

10. Sexual excitement in animals.

11. Fermentation.

Animal heat, Blood heat, Capacity for heat, etc. See under Animal, Blood, etc.

Atomic heat (Chem.), the product obtained by multiplying the atomic weight of any element by its specific heat. The atomic heat of all solid elements is nearly a constant, the mean value being 6.4.

Dynamical theory of heat, that theory of heat which assumes it to be, not a peculiar kind of matter, but a peculiar motion of the ultimate particles of matter.

Heat engine, any apparatus by which a heated substance, as a heated fluid, is made to perform work by giving motion to mechanism, as a hot-air engine, or a steam engine.

Heat producers. (Physiol.) See under Food.

Heat rays, a term formerly applied to the rays near the red end of the spectrum, whether within or beyond the visible spectrum.

Heat weight (Mech.), the product of any quantity of heat by the mechanical equivalent of heat divided by the absolute temperature; -- called also thermodynamic function, and entropy.

Mechanical equivalent of heat. See under Equivalent.

Specific heat of a substance (at any temperature), the number of units of heat required to raise the temperature of a unit mass of the substance at that temperature one degree.

Unit of heat, the quantity of heat required to raise, by one degree, the temperature of a unit mass of water, initially at a certain standard temperature. The temperature usually employed is that of 0[deg] Centigrade, or 32[deg] Fahrenheit.

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