Origin of re-act

First recorded in 1650–60; re- + act


verb (used without object)
  1. to act in response to an agent or influence: How did the audience react to the speech?
  2. to act reciprocally upon each other, as two things.
  3. to act in a reverse direction or manner, especially so as to return to a prior condition.
  4. to act in opposition, as against some force.
  5. to respond to a stimulus in a particular manner: reacting to a shock by jumping; to react to the word “coward” with anger.
  6. to undergo a chemical reaction.

Origin of react

1635–45; re- + act, probably modeled on Medieval Latin reagere Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for reacting

Contemporary Examples of reacting

Historical Examples of reacting

  • Shann sped on, reacting to a plea which did not lay in the words themselves.

    Storm Over Warlock

    Andre Norton

  • And the anguish of that thought, reacting on his anger, intensified it threefold.

    The Island Pharisees

    John Galsworthy

  • Let's have it before I hit rock-bottom and really get around to reacting.

    The Short Life

    Francis Donovan

  • They were surprisingly ready, reacting like hair-triggered weapons.

    Talents, Incorporated

    William Fitzgerald Jenkins

  • Reacting to it, she took Bill by the arm and shook it roughly.


    Frank Bacon

British Dictionary definitions for reacting


  1. (intr ; foll by to, upon etc) (of a person or thing) to act in response to another person, a stimulus, etc, or (of two people or things) to act together in a certain way
  2. (intr foll by against) to act in an opposing or contrary manner
  3. (intr) physics to exert an equal force in the opposite direction to an acting force
  4. chem to undergo or cause to undergo a chemical reaction

Word Origin for react

C17: from Late Latin reagere, from re- + Latin agere to drive, do


  1. (tr) to act or perform again
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 reacting



1640s, "to exert, as a thing acted upon, an opposite action upon the agent," from re- + act (v.). Chemical sense is from 1944. Related: Reacted; reacting (1610s). For sense development, see reaction. Meaning "perform again" (often re-act) is from 1650s.

Online Etymology Dictionary, © 2010 Douglas Harper

reacting in Medicine


  1. To act in response to a stimulus.
  2. To undergo a chemical reaction.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.