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

Even some creators being paid to love their estrogen creams are fairly measured when reporting their results, which include less reactivity and more hydration. — Ashley Abramson, Allure, 22 Oct. 2026

As the test progressed, the team recorded a subcritical reactivity measurement at a peak core temperature of 1,852°F. — Aman Tripathi, Interesting Engineering, 22 Oct. 2026

The researchers also reported that giving testosterone after injury reduced the excessive cardiovascular reactivity caused by traumatic brain injury in their model. — Samantha Agate, Miami Herald, 19 Oct. 2026

The Wayne State 2025 study also found that administering testosterone after injury reduced excessive cardiovascular reactivity induced by traumatic brain injury. — Samantha Agate, Kansas City Star, 19 Oct. 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