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 The news about Bickle on Friday night drew swift reaction from former IHOPKC leaders. Judy L. Thomas, Kansas City Star, 25 Mar. 2024 Waronker: Going back to college and having an invasive leg surgery — that’s a weird reaction to success. Mikael Wood, Los Angeles Times, 25 Mar. 2024 Camila proved to have an alluring sound with vocals fit for a Latin pop star, becoming more confident throughout the performance and even looking at her father at one point to see his reaction. Sadie Bell, Peoplemag, 25 Mar. 2024 Since Quiet on Set premiered last week, reactions to the docuseries from Schneider himself and those who worked with him have been made public, with many condemning the behavior and others sharing their bad workplace experiences. Kevin Dolak, The Hollywood Reporter, 25 Mar. 2024 As knee-jerk reactions to AI faded over the course of the year, new theories cropped up about AI’s trajectory. Chloe Berger, Fortune, 25 Mar. 2024 The immediate reaction in leftist circles was harsh. David Peisner, Rolling Stone, 24 Mar. 2024 In mixed chat groups, pictures and videos get pixelated, messages can take longer to send or not send at all, and reactions are written out instead of displayed as reaction icons, among many other annoying issues. Jody Serrano, Quartz, 23 Mar. 2024 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

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 29 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

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!