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

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

One patient retained normal core disgust reactivity but could no longer recognize disgust in others’ faces; another with anterior insula damage showed dysregulation in both producing and experiencing disgust. —Scott Travers, Forbes.com, 16 May 2026

This helped secure the first of two recent wins that have given Arsenal breathing space at the top of the table and highlighted Raya’s balance, reactivity and ability to reorganise his body against an unpredictable strike. —Matt Pyzdrowski, New York Times, 10 May 2026

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

Word History

First Known Use

1832, in the meaning defined above

Phrases Containing reactivity

• hyper-reactivity

Rhymes for reactivity

• acclivity
• activity
• captivity
• declivity
• festivity
• nativity
• passivity
• proclivity
• absorptivity
• affectivity
• collectivity
• conductivity

Medical 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