What does exothermal mean?
Exothermal is a technical adjective describing a reaction, process, or other change that releases heat to its surroundings. It is especially common in discussions of chemical reactions, nuclear processes, and physical transformations. An exothermal process gives off energy, so the products of the reaction generally possess less energy than the starting materials. The opposite is an endothermic process, which absorbs energy, often as heat, from its surroundings. Exothermal and exothermic are close equivalents, but exothermic has become the more usual term in modern chemistry. Knowing the distinction is useful when interpreting heat flow, assessing the energy efficiency of a reaction, or comparing processes such as combustion with reactions that require a continuous input of heat. The word is relatively uncommon in everyday speech but firmly established in scientific and technical prose.
adjectiveRelating to the release of heat or energy to the surroundings. In chemistry, an exothermal reaction releases heat as it proceeds, whereas an endothermic reaction absorbs heat.
- Relating to the release of heat or energy to the surroundings.
"The exothermal reaction warmed the water almost to the boiling point."
"Combustion is an exothermal process that releases heat and light."
"Researchers measured the temperature change during the exothermal reaction."
Exothermal puts the heat on the outside: it names a process that releases energy rather than absorbing it.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does exothermal come from?
Exothermal is a modern English technical compound formed from the combining form exo-, derived from Greek exō, meaning “outside” or “outward from,” and thermal, based on Greek thermē, meaning “heat.” The term developed to indicate the outward release of heat associated with an exothermic process. Related English formations include exothermic, which uses the same exo- and heat components, while exosphere and exogenous preserve the Greek exō element and thermal, thermic, and isothermal preserve the therm- element.
Related word forms
How exothermal is actually used
Chiefly used in technical contexts, especially chemistry, physics, and earth sciences. It is nearly synonymous with “exothermic,” although “exothermic” is more common in contemporary scientific writing.
Easily confused with exothermal
Both terms describe a process that releases energy as heat, but “exothermic” is the more usual modern term in chemistry.