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

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

Researchers revealed that this methodology resolves spatial variations in photocatalytic reactivity of nanoscale cocatalysts supported on semiconductors with a spatial resolution on the order of 10 nm. —Prabhat Ranjan Mishra, Interesting Engineering, 3 Apr. 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

Despite their distinct appearances, both sides are exactly the same in terms of function and reactivity with food. —Darcy Lenz, Southern Living, 17 Feb. 2026

Word History

First Known Use

1832, in the meaning defined above

Phrases Containing reactivity

• hyper-reactivity

Rhymes for reactivity

• absorptivity
• affectivity
• collectivity
• conductivity
• connectivity
• corrosivity
• creativity
• diffusivity
• directivity
• effectivity
• emissivity
• exclusivity

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