re·​ac·​tiv·​i·​ty | \ (ˌ)rē-ˌak-ˈti-və-tē How to pronounce reactivity (audio) \

Definition of reactivity

: the quality or state of being reactive emotional reactivity chemical reactivity If the brain, responding to psychological stress, stimulates the release of cortisol and cortisol suppresses the reactivity of the immune system, then a dormant viral infection may well flare up, or a new one catch hold.— Matt Ridley Abnormal reactivity to light and abnormal pupillary size may be important clues to the presence of cranial injury in the setting of head trauma.— Bradford J. Shingleton

Examples of reactivity in a Sentence

Recent Examples on the Web There has been no convincing evidence so far for any protective effect of T cell cross-reactivity. David Hogberg, Washington Examiner, "Some people may have preexisting immunity to the coronavirus," 17 Dec. 2020 Its high reactivity with oxygen urges it to form compounds, including silicates (like clay) and silica (like quartz). David Lumb, Popular Mechanics, "109 Ways Silicon Completely Rules Every Part of Your Life," 9 Dec. 2020 Perpetrators of such behavior tend to be younger, male, and high in emotional reactivity and impulsivity. Wired Opinion, Wired, "Toxicity in Gaming Is Dangerous. Here's How to Stand Up to It," 9 Dec. 2020 This point does reference a really positive finding: many people do have T-cell reactivity to this coronavirus, meaning a piece of their immune system kicks into gear because this virus is in some ways similar to past ones. Andy Larsen, The Salt Lake Tribune, "Busting coronavirus myths found on social media," 6 Oct. 2020 Third, the strength of T cell reactivity in people recovering from COVID-19 appears to be inversely proportional to disease severity; while there are exceptions, most people with a strong T cell response experience mild symptoms or none at all. Kevin Esvelt, Scientific American, "Could Exposure to the Common Cold Reduce the Severity of COVID-19 Infection?," 28 Sep. 2020 Stress also increases levels of cortisol, which Dr. Saltz says can increase hypersensitivity and reactivity to a challenging or stressful situation. Alexis Hobbs, Woman's Day, "Why Do I Cry So Easily? Experts Break Down the Reasons Behind Your Tears," 9 Sep. 2020 In a cycle of reactivity, ordinary people turn not to social democracy—now at its weakest point since World War II—but to the vicarious and counterfeit satisfactions of extreme nationalism. Robert Kuttner, The New York Review of Books, "Can We Fix Capitalism?," 8 Sep. 2020 T cell reactivity suggests that the immune system might have had some previous experience fighting a similar infection and may use that memory to help fight a new infection. Ivana Kottasová, CNN, "What you need to know about coronavirus on Friday, July 31," 31 July 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'reactivity.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of reactivity

1832, in the meaning defined above

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Time Traveler for reactivity

Time Traveler

The first known use of reactivity was in 1832

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Statistics for reactivity

Last Updated

31 Dec 2020

Cite this Entry

“Reactivity.” Dictionary, Merriam-Webster, Accessed 21 Jan. 2021.

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More Definitions for reactivity


re·​ac·​tiv·​i·​ty | \ (ˌ)rē-ˌak-ˈtiv-ət-ē How to pronounce reactivity (audio) \
plural reactivities

Medical Definition of reactivity

: the quality or state of being reactive skin reactivity emotional reactivity

Comments on reactivity

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