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 of react

• 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

Wall Street, which is accustomed to robust growth from Walmart, reacted swiftly to the lukewarm sales numbers, and the company’s stock plunged 9% Thursday. — Kayla Steinberg, NBC news, 20 Aug. 2026

Washington and Seoul say their drills are defensive in nature, but North Korea calls them an invasion rehearsal and often reacts with weapons tests. — Hyung-Jin Kim, Los Angeles Times, 20 Aug. 2026

His video of Wilbur has gained thousands of views and comments from people reacting to the excursion. — Chelsea Hylton, CBS News, 20 Aug. 2026

In addition, co-star Kim Coates released a statement reacting to Legends. — James Hibberd, HollywoodReporter, 20 Aug. 2026

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

• act
• backed
• blacked
• bract
• cracked
• fact
• hacked
• jacked
• lacked
• packed
• pact
• racked

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