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exothermic

American  
[ek-soh-thur-mik] / ˌɛk soʊˈθɜr mɪk /
Or exothermal

adjective

Chemistry.
  1. noting or pertaining to a chemical change that is accompanied by a liberation of heat (opposed to endothermic).


exothermic British  
/ ˌɛksəʊˈθɜːmɪk /

adjective

  1. (of a chemical reaction or compound) occurring or formed with the evolution of heat Compare endothermic exoergic

"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

exothermic Scientific  
/ ĕk′sō-thûrmĭk /
  1. Relating to a chemical reaction that releases heat.

  2. Compare endothermic


Other Word Forms

  • exothermally adverb
  • exothermically adverb
  • exothermicity noun

Etymology

Origin of exothermic

First recorded in 1880–85; exo- + thermic

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Explanation

In chemistry, something that's exothermic has to do with the release of heat. Burning a candle is an exothermic process, since heat is given off. The scientific adjective exothermic is good for describing reactions that involve releasing energy, usually in the form of heat. Exothermic processes vary from something as simple as striking a match on a rough surface to a more extreme and violent example — an explosion. Part of what defines an exothermic reaction is that more energy is released than was required to start it. The word's Greek roots are exo, "outside," and therme, "heat."

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

If the reaction is exothermic, the heat produced can be thought of as a product.

From Textbooks • Feb. 14, 2019

Sulfur trioxide forms slowly when heating sulfur dioxide and oxygen together, and the reaction is exothermic:

From Textbooks • Feb. 14, 2019

This condition describes an exothermic process that involves a decrease in system entropy.

From Textbooks • Feb. 14, 2019

Among other things, an ideal fuel for the control thrusters of a space vehicle should decompose in a spontaneous exothermic reaction when exposed to the appropriate catalyst.

From Textbooks • Feb. 14, 2019

“The water creates an exothermic reaction—do you feel it warming up?”

From "The Running Dream" by Wendelin Van Draanen