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

• 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

Instead of reacting out of habit, curious individuals ask questions like What is the most important task right now? —Dr. Diane Hamilton, Forbes.com, 1 July 2025

Manager Alex Cora reacts after a double play in the fifth inning against the Los Angeles Angels at Angel Stadium of Anaheim on June 23, 2025 in Anaheim, California. —Jon Vankin, MSNBC Newsweek, 30 June 2025

In a statement to Variety, the Recording Industry Association of America (RIAA) reacted to the Supreme Court news, first reported by Reuters. —Andrew Flanagan, Variety, 30 June 2025

Investors will only have half a day to react: U.S. markets close early Thursday and are dark Friday. —Yeo Boon Ping, CNBC, 30 June 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

Rhymes for react

• abstract
• attacked
• attract
• contact
• contract
• detract
• distract
• enact
• exact
• extract
• hijacked
• impact

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