reaction

noun

re·​ac·​tion rē-ˈak-shən How to pronounce reaction (audio)
1
a
: the act or process or an instance of reacting
b
: resistance or opposition to a force, influence, or movement
especially : tendency toward a former and usually outmoded political or social order or policy
2
: a response to some treatment, situation, or stimulus
her stunned reaction to the news
also : such a response expressed verbally
critical reaction to the play
3
: bodily response to or activity aroused by a stimulus:
a
: an action induced by vital resistance to another action
especially : the response of tissues to a foreign substance (such as an antigen or infectious agent)
b
: depression or exhaustion due to excessive exertion or stimulation
c
: heightened activity and overaction succeeding depression or shock
d
: a mental or emotional disorder forming an individual's response to his or her life situation
4
: the force that a body subjected to the action of a force from another body exerts in the opposite direction
5
a(1)
: chemical transformation or change : the interaction of chemical entities
(2)
: the state resulting from such a reaction
b
: a process involving change in atomic nuclei

Examples of reaction in a Sentence

Their reaction to the news was positive. When I told him what happened, his immediate reaction was one of shock. The announcement produced an angry reaction from most of the people at the meeting. My first reaction when I met him was not to trust him. There hasn't yet been much reaction to the announcement. There has been strong reaction against the government's policies. A good driver has quick reactions. The speed of his reactions saved his life.
Recent Examples on the Web Alexander was shut down after suffering a left rib stress reaction that team is calling a deep bruise. Jon Becker, The Mercury News, 14 Mar. 2024 To mark this momentous occasion, the Glamour staff got together (via Slack) to watch the reunion, sharing all of our reactions and hot takes in real time. Glamour, 14 Mar. 2024 Overall, the Senate's reaction to the House bill has been mixed. Caitlin Yilek, CBS News, 14 Mar. 2024 People are going to walk away having an extreme reaction to it, and that’s all her. William Earl, Variety, 13 Mar. 2024 Coaches offer dueling reactions after LSU-South Carolina near-brawl The ugliness that marred the end of the SEC tournament title game Sunday afternoon called for restraint, common sense and a dose of humility from both coaches. USA TODAY, 12 Mar. 2024 One fan pointed out that Across the Spider-Verse co-writer Christopher Miller and producer had the proper reaction. Tatiana Tenreyro, The Hollywood Reporter, 11 Mar. 2024 Here are some of our other favorite online reactions to the (puff, puff, pass) palindrome. Grace Tucker, The Enquirer, 11 Mar. 2024 Now, Dune: Part Two (March 1) is poised to be his new top grosser after effusive early reactions and reviews. Brian Davids, The Hollywood Reporter, 1 Mar. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'reaction.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1585, in the meaning defined at sense 1a

Time Traveler
The first known use of reaction was in 1585

Dictionary Entries Near reaction

Cite this Entry

“Reaction.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/reaction. Accessed 28 Mar. 2024.

Kids Definition

reaction

noun
re·​ac·​tion rē-ˈak-shən How to pronounce reaction (audio)
1
a
: the act or process or an instance of reacting
our reaction to the news
b
: an action or attitude opposing current political or social forces or ideas
2
: a bodily response to a stimulus
especially : the response of the body to a foreign substance (as a drug)
3
: the force that opposes the action of a force applied to one body by another body
4
a
: chemical transformation or change : the action between atoms or molecules to form one or more new substances
b
: a process involving change in atomic nuclei

Medical Definition

reaction

noun
re·​ac·​tion rē-ˈak-shən How to pronounce reaction (audio)
1
: the act or process or an instance of reacting
2
: bodily response to or activity aroused by a stimulus:
a
: an action induced by vital resistance to another action
especially : the response of tissues to a foreign substance (as an antigen or infectious agent)
b
: depression or exhaustion due to excessive exertion or stimulation
c
: abnormally heightened activity succeeding depression or shock
d
: a mental or emotional disorder forming an individual's response to his or her life situation
3
: the force that a body subjected to the action of a force from another body exerts in the opposite direction
4
a(1)
: chemical transformation or change : the interaction of chemical entities
(2)
: the state resulting from such a reaction
b
: a process involving change in atomic nuclei

More from Merriam-Webster on reaction

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