What does "react" mean?

1. (to respond to something) to change your behaviour or feelings because of something that happens. 2. (chemical change) to change when mixed with another substance. 3. (social media response) to use an emoji or icon to show how you feel about a post online. 4. (an emoji response) an emoji or icon used to show a feeling on social media.

Is it correct to say "He reacted at the news by crying."?

No — say "He reacted to the news by crying.". The verb 'react' is followed by the preposition 'to' when identifying the cause of the response.

react

v. · n.

US //ɹiˈækt// UK //ɹɪˈækt// re·act

1 to respond to something (v.)
A2 Elementary

to change your behaviour or feelings because of something that happens.

to act in response to a stimulus, event, or situation. Intransitive; typically takes the preposition 'to'.

Example

How did your parents react when you told them you were moving?

Example

The markets reacted sharply to the central bank's announcement, with stock prices falling within minutes of the press conference.
- ignore
Pitfall

He reacted at the news by crying.

He reacted to the news by crying.

The verb 'react' is followed by the preposition 'to' when identifying the cause of the response.
2 chemical change (v.)
B2 Upper Intermediate Technical Science

to change when mixed with another substance.

to undergo a chemical change when in contact with another substance or energy source. Often used with 'with'.

Example

The acid will react with the metal and create small bubbles.

Example

When the two compounds react under high pressure, they form a stable polymer that is resistant to heat.
- transform
- interact

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3 social media response (v.)
B1 Intermediate Informal Computing

to use an emoji or icon to show how you feel about a post online.

to post a digital reaction, such as an emoji, to indicate a specific emotional response to a message or post.

Example

I didn't have time to reply, so I just reacted with a heart emoji.

Example

Users can now react to individual messages in the thread, allowing for quicker feedback without cluttering the conversation with text.
- interact
- reply
4 an emoji response (n.)
B2 Upper Intermediate Slang Informal Computing

an emoji or icon used to show a feeling on social media.

a specific emoji or symbolic icon selected by a user to express a sentiment toward a digital post.

Example

The post got over a hundred likes and several angry reacts.

Example

The community manager noted that the 'laugh' react was being used sarcastically on the company's official announcement.
- emoji
- interaction

Origin

From re- + act. Piecewise doublet of redact.

Word family

Verboverreact
Verbreact
Nounreactor
Adjectivereactive