1. the quality or condition of being reactive.
  2. Chemistry. the relative capacity of an atom, molecule, or radical to undergo a chemical reaction with another atom, molecule, or compound.
  3. Physics. a measure of the deviation from the condition at which a nuclear reactor is critical.
  4. Immunology. the ability of an antigen to combine with an antibody.

Origin of reactivity

First recorded in 1885–90; reactive + -ity
Related formshy·per·re·ac·tiv·i·ty, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

reactivities in Medicine


  1. The property of reacting.
  2. The process of reacting.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.