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

Stefanik campaign reacts Stefanik's campaign released a lengthy statement addressing Blakeman's apparent quest for the Executive Mansion in Albany. —Mark Prussin, CBS News, 8 Dec. 2025

How did the public react to John Lennon’s death? —Nicole Briese, PEOPLE, 8 Dec. 2025

The pro-safety crowd has also reacted to the growing tensions. —Max Tani, semafor.com, 8 Dec. 2025

This is especially true for acidic foods like tomatoes, which can react with cans over time, causing taste and texture changes. —Katie Rosenhouse, Southern Living, 7 Dec. 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