tending to react.
pertaining to or characterized by reaction.
Electricity. pertaining to or characterized by reactance.

Origin of reactive

First recorded in 1705–15; react + -ive
Related formsre·ac·tive·ly, adverbre·ac·tive·ness, nounan·ti·re·ac·tive, adjectivehy·per·re·ac·tive, adjectivenon·re·ac·tive, adjectiveo·ver·re·ac·tive, adjectiveun·re·ac·tive, adjective
Can be confusedproactive reactionary reactive Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for reactive

Contemporary Examples of reactive

Historical Examples of reactive

  • They rise and fall together; they are reactive, one upon the other.

  • Succedaneum for Chrysarobin; very active reducer or "reactive."

    Merck's 1899 Manual

    Merck & Co.

  • The bandolero was languishing in the third reactive stage of malignant cholera.

    The Wolf Cub

    Patrick Casey

  • But they had been replaced by an uncontrollable, reactive nausea.


    Daniel F. Galouye

  • But there are many possible tracer rays not reactive to a screen such as I was using.

    Skylark Three

    Edward Elmer Smith

British Dictionary definitions for reactive



readily partaking in chemical reactionssodium is a reactive metal; free radicals are very reactive
of, concerned with, or having a reactance
responsive to stimulus
(of mental illnesses) precipitated by an external causereactive depression
Derived Formsreactively, adverbreactivity (ˌriːækˈtɪvɪtɪ) or reactiveness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for reactive

1712, from react + -ive. Related: Reactively; reactiveness; reactivity.

Online Etymology Dictionary, © 2010 Douglas Harper

reactive in Medicine




Tending to be responsive or to react to a stimulus.
Characterized by reaction.
Tending to participate readily in chemical reactions.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.