[ en-thal-pee, en-thal- ]
/ ˈɛn θæl pi, ɛnˈθæl- /
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noun, plural en·thal·pies.Thermodynamics.
a quantity associated with a thermodynamic system, expressed as the internal energy of a system plus the product of the pressure and volume of the system, having the property that during an isobaric process, the change in the quantity is equal to the heat transferred during the process. Symbol: H


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Also called heat content, total heat.

Origin of enthalpy

1925–30; <Greek enthálp(ein) to warm in (en-en-2 + thálpein to warm) + -y3
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

British Dictionary definitions for enthalpy

/ (ˈɛnθəlpɪ, ɛnˈθæl-) /

a thermodynamic property of a system equal to the sum of its internal energy and the product of its pressure and volumeSymbol: H Also called: heat content, total heat

Word Origin for enthalpy

C20: from Greek enthalpein to warm in, from en- ² + thalpein to warm
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 enthalpy

[ ĕnthăl′pē ]

A partial measure of the internal energy of a system. Enthalpy cannot be directly measured, but changes in it can be. If an outside pressure on a system is held constant, a change in enthalpy entails a change in the system's internal energy, plus a change in the system's volume (meaning the system exchanges energy with the outside world). For example, in endothermic chemical reactions, the change in enthalpy is the amount of energy absorbed by the reaction; in exothermic reactions, it is the amount given off. See also thermodynamics.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.