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See more synonyms for reactive on Thesaurus.com
  1. tending to react.
  2. pertaining to or characterized by reaction.
  3. Electricity. pertaining to or characterized by reactance.
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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
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for reactive

sympathetic, sensible, conscious, susceptible, receptive, compassionate, aware, sensitive, active, reactive, tricky, precise, tense, keen, nervous, touchy, perceptive, unstable, delicate, responsive

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  • But they had been replaced by an uncontrollable, reactive nausea.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


  1. readily partaking in chemical reactionssodium is a reactive metal; free radicals are very reactive
  2. of, concerned with, or having a reactance
  3. responsive to stimulus
  4. (of mental illnesses) precipitated by an external causereactive depression
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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.

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Online Etymology Dictionary, © 2010 Douglas Harper

reactive in Medicine


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