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Synonyms

reactant

American  
[ree-ak-tuhnt] / riˈæk tənt /

noun

  1. a person or thing that reacts.

  2. Also called interactant.  Chemistry. any substance that undergoes a chemical change in a given reaction.

reactant British  
/ rɪˈæktənt /

noun

  1. a substance that participates in a chemical reaction, esp a substance that is present at the start of the reaction Compare product

"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
reactant Scientific  
/ rē-ăk′tənt /

  1. A substance participating in a chemical reaction, especially one present at the start of the reaction.

Etymology

Origin of reactant

First recorded in 1925–30; react + -ant

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.

By adjusting the chemical composition and pH of the reactant solutions, they altered both the size and properties of the ultrasmall openings.

From Science Daily • Feb. 19, 2026

Once the temperature is sufficiently low, the concentration of the reactant gases on the catalyst surface increases and the reaction picks up speed again.

From Science Daily • Oct. 5, 2023

That is, as the temperature of the reaction goes up due to its heat production, the reactant gases lose contact with the catalyst surface and their reaction slows down, which reduces the temperature.

From Science Daily • Oct. 5, 2023

This important reaction class is defined by changes in oxidation states for one or more reactant elements, and it includes a subset of reactions involving the transfer of electrons between reactant species.

From Textbooks • Feb. 14, 2019

They cool the reactant fuel to keep it from getting too hot and wildcatting.

From Treachery in Outer Space by Glanzman, Louis

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.