react

verb

re·​act rē-ˈakt How to pronounce react (audio)
reacted; reacting; reacts

intransitive verb

1
: to exert a reciprocal or counteracting force or influence
often used with on or upon
2
: to change in response to a stimulus
3
: to act in opposition to a force or influence
usually used with against
4
: to move or tend in a reverse direction
5
: to undergo chemical reaction

transitive verb

: to cause to react

Examples of react in a Sentence

When I told her what happened, she reacted with anger. I didn't expect him to react that way. The firefighters reacted quickly when they heard the alarm. He reacted badly to the drug.
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Their objective was to replicate the intricacy of nature in artificial systems that can see and react to their environment—an accomplishment that has long been regarded as challenging at such small sizes. Jijo Malayil, Interesting Engineering, 20 Oct. 2025 Hostin and her fellow View cohosts reacted to the video during Monday’s episode. Emlyn Travis, Entertainment Weekly, 20 Oct. 2025 Bondi reacted to the sketch by embracing her depiction. Brendan Morrow, USA Today, 19 Oct. 2025 The example below from the 24th minute showed how that freed up Sangare, with Santos, who reacts in frustration, and Lavia outnumbered. Anantaajith Raghuraman, New York Times, 19 Oct. 2025 See All Example Sentences for react

Word History

Etymology

New Latin reactus, past participle of reagere, from Latin re- + agere to act — more at agent

First Known Use

1644, in the meaning defined at intransitive sense 1

Time Traveler
The first known use of react was in 1644

Cite this Entry

“React.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/react. Accessed 24 Oct. 2025.

Kids Definition

react

verb
re·​act rē-ˈakt How to pronounce react (audio)
1
: to act or behave in response (as to stimulation or an influence)
the colonists reacted to the tax by boycotting tea
2
: to oppose a force or influence
usually used with against
reacted against their unfair treatment
3
: to go through or cause to go through a chemical reaction

Medical Definition

react

intransitive verb
re·​act rē-ˈakt How to pronounce react (audio)
1
: to respond to a stimulus
2
: to undergo chemical reaction

transitive verb

: to cause to react

More from Merriam-Webster on react

Last Updated: - Updated example sentences
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