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

Example Sentences

Recent Examples on the Web The prediction would be that any regions of the brain having to do with emotional reactivity, like the amygdala and hypothalamus, or with controlling aggressive responses, such as the prefrontal cortex, should be really different. Matthew Hutson, Discover Magazine, 31 July 2011 Thorell's test is called electrodermal orientation reactivity (aka electrodermal hyporeactivity), and while Thorell's work on the technique goes back to the 1980s, it has recently been commercialized by a company called Emotra AB, who named the product EDOR®. Neuroskeptic, Discover Magazine, 5 Dec. 2017 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, 24 Sep. 2020 In addition to working on impulse control and reactivity, Ralphie is also engaging in agility training, according to the Facebook post. Zoe Sottile, CNN, 4 Mar. 2023 Start by shifting your mindset on leadership and reactivity. Forbes, 27 Jan. 2023 The University of Michigan researchers found that the use of devices to calm boys and children with high temperamental surgency (like hyperactivity or impulsiveness) was associated with higher emotional reactivity. Carla Delgado, Discover Magazine, 26 Jan. 2023 Arousal and reactivity symptoms relate to a person feeling on guard or daily activities such as sleeping or concentrating on a task. Claire Gillespie, Health, 21 Jan. 2023 While Hanks gives Parker a giddy skip to his step, Butler is nearly stone-faced, leaning into kiss after kiss with little reactivity. Vulture, 2 Sep. 2022 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'reactivity.' 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

1832, in the meaning defined above

Time Traveler
The first known use of reactivity was in 1832

Dictionary Entries Near reactivity

Cite this Entry

“Reactivity.” Dictionary, Merriam-Webster, Accessed 4 Jun. 2023.

Medical Definition


re·​ac·​tiv·​i·​ty (ˌ)rē-ˌak-ˈtiv-ət-ē How to pronounce reactivity (audio)
plural reactivities
: the quality or state of being reactive
skin reactivity
emotional reactivity
Last Updated: - Updated example sentences
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