react Definition

react
verb reacted, reacting

intr
1a. To act in response to something said or done, or to another person;

Thesaurus: respond, reply, reciprocate, answer, counter, requite, offset.
Form: react to something (chiefly)
Form: react to someone
intr
1b. loosely
To act or behave.
Thesaurus: behave, function, act.
intr
2a. To respond to it in a way which shows dislike or disapproval;

Form: react against something (usually)
intr
2b. To act in a contrary or opposing way.

Form: react against something (usually)
intr
3. physics.
To exert an equal force in the opposite direction.
4. chem.
To undergo or cause to undergo chemical change produced by a reagent.
intr
5. stock exchange.
Said of share prices: to fall sharply after a rise.

Etymology: 17c: from Latin reagere, reactum, from agere to do or act.