react

verb

re·​act rē-ˈakt 

reacted; reacting; reacts

intransitive verb

1

: to exert a reciprocal or counteracting force or influence

—often used with on or upon

2

: to change in response to a stimulus

3

: to act in opposition to a force or influence

—usually used with against

4

: to move or tend in a reverse direction

5

: to undergo chemical reaction

transitive verb

: to cause to react

Synonyms

• reply
• respond

Examples of react in a Sentence

When I told her what happened, she reacted with anger.

I didn't expect him to react that way.

The firefighters reacted quickly when they heard the alarm.

He reacted badly to the drug.

Recent Examples on the Web

Traffic to McDonald’s restaurants across the U.S. fell as consumers reacted to the headlines, although analysts expect the company to report that trend reversed later in the quarter. —Amelia Lucas, CNBC, 28 Jan. 2025

Selena Gomez slammed a Republican politician who said she should be deported after sharing an emotional video appearing to react to President Donald Trump's recent immigration crackdown earlier this week. —Kimberlee Speakman, People.com, 28 Jan. 2025

The injury immediately raised concerns, with commentators and fans alike reacting with visible worry. —Barbara A. Perry, Newsweek, 28 Jan. 2025

Kansas City reacted accordingly by shading its biggest bodies to that side. —Sam Farmer, Los Angeles Times, 27 Jan. 2025

Word History

Etymology

New Latin reactus, past participle of reagere, from Latin re- + agere to act — more at agent

First Known Use

1644, in the meaning defined at intransitive sense 1

Phrases Containing react

• react against

Kids Definition

react

verb

re·​act rē-ˈakt 

1

: to act or behave in response (as to stimulation or an influence)

the colonists reacted to the tax by boycotting tea

2

: to oppose a force or influence

—usually used with against

reacted against their unfair treatment

3

: to go through or cause to go through a chemical reaction

Medical Definition

react

intransitive verb

re·​act rē-ˈakt 

1

: to respond to a stimulus

2

: to undergo chemical reaction

transitive verb

: to cause to react