reactivity
noun
re·ac·tiv·i·ty
(ˌ)rē-ˌak-ˈti-və-tē 
: 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
Matt RidleyAbnormal 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
Bradford J. ShingletonExamples of reactivity in a Sentence
Recent Examples on the Web
It is first pulverized into a fine powder, then dried, purified, and treated at the surface to optimize its reactivity.
—Bojan Stojkovski, Interesting Engineering, 26 Apr. 2026
Dogs bred for alertness or reactivity may be more attuned to sound, though this isn’t a hard-and-fast rule.
—Jamie Cuccinelli, Martha Stewart, 7 Apr. 2026
But research by Mark Wetherell, a professor of psychobiology and health psychology, has shown that the mere expectation of social evaluation produces anticipatory stress reactivity — meaning the body begins responding before the evaluative event even occurs.
—Amy Cuddy, New York Times, 28 Mar. 2026
Detecting and measuring hydrogen underground is difficult because of its small molecular size and reactivity with other elements in the rocks.
—Promise Longe, The Conversation, 26 Feb. 2026
See All Example Sentences for reactivity
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Bojan Stojkovski, Interesting Engineering, 26 Apr. 2026
Dogs bred for alertness or reactivity may be more attuned to sound, though this isn’t a hard-and-fast rule.
—Jamie Cuccinelli, Martha Stewart, 7 Apr. 2026
But research by Mark Wetherell, a professor of psychobiology and health psychology, has shown that the mere expectation of social evaluation produces anticipatory stress reactivity — meaning the body begins responding before the evaluative event even occurs.
—Amy Cuddy, New York Times, 28 Mar. 2026
Detecting and measuring hydrogen underground is difficult because of its small molecular size and reactivity with other elements in the rocks.
—Promise Longe, The Conversation, 26 Feb. 2026
See All Example Sentences for reactivity
Cite this Entry
“Reactivity.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/reactivity. Accessed 3 May. 2026.
Copy CitationMedical Definition
reactivity
noun
re·ac·tiv·i·ty
(ˌ)rē-ˌak-ˈtiv-ət-ē
plural reactivities
: the quality or state of being reactive
skin reactivity
emotional reactivity
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