verb (used without object)

to act in response to an agent or influence: How did the audience react to the speech?
to act reciprocally upon each other, as two things.
to act in a reverse direction or manner, especially so as to return to a prior condition.
to act in opposition, as against some force.
to respond to a stimulus in a particular manner: reacting to a shock by jumping; to react to the word “coward” with anger.
to undergo a chemical reaction.

Origin of react

1635–45; re- + act, probably modeled on Medieval Latin reagere



verb (used with object)

to act or perform again.

Origin of re-act

First recorded in 1650–60; re- + act Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for react

Contemporary Examples of react

Historical Examples of react

  • Previously, this dog did not react when it saw people stoop down.

  • There is thus no domain of the mind which is not influenced by love, and which does not react on love in its turn.

  • At any rate he will then be less often deceived and will react in a more plastic manner.

  • But the children are well aware of this fact, consciously or not, and react accordingly.

  • "That's why you react so strongly from love in your plays," Roger said judicially.

    Changing Winds

    St. John G. Ervine

British Dictionary definitions for react



(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
(intr foll by against) to act in an opposing or contrary manner
(intr) physics to exert an equal force in the opposite direction to an acting force
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



(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 react

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

react in Medicine




To act in response to a stimulus.
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.