Reaction

riˈækʃən

nounBeginnerVery CommonScience

Definitions

3 meanings
1

An action performed or a feeling experienced in response to a situation or event.

riˈækʃən

nounneutralBeginner
Science

A response to something

Her initial reaction was shock, but she quickly composed herself.

💡 Simply: Imagine someone tells you a funny joke. Your reaction might be to laugh. It's what you do or how you feel *because* of something else.

👶 For kids: When something happens, like a ball bouncing, what happens next is called a reaction.

More Examples

2

The government's reaction to the crisis was slow and inadequate.

3

The team's reaction to the coach's criticism was to work harder.

How It's Used

General

"Her reaction to the news was one of surprise."

Chemistry

"The chemical reaction produced a gas."

Physics

"Newton's third law of motion states that for every action, there is an equal and opposite reaction."

Psychology

"His reaction was a clear sign of his underlying anxiety."

2

A process in which one or more substances are changed into others.

riˈækʃən

nounneutralmedium
Science

A chemical process

The chemical reaction released heat and light.

💡 Simply: In chemistry, when things mix and change, like baking a cake. The ingredients 'react' to make the cake.

👶 For kids: When you mix things together and they change, like mixing baking soda and vinegar, that's a reaction.

More Examples

2

An allergic reaction caused a rash.

3

The scientist carefully monitored the reaction in the test tube.

How It's Used

Chemistry

"The reaction produced a precipitate."

Biology

"An allergic reaction to pollen."

Medicine

"Adverse reaction to the drug."

Tip:Think of ingredients combining to form a new product.
3

A political or social movement opposing progress or reform.

riˈækʃən

nounnegativemedium
Legal

Political opposition

There was a strong reaction against the proposed legislation.

💡 Simply: Imagine someone tries to change something (like a new law), and some people strongly disagree and try to stop it. That's a reaction.

👶 For kids: Sometimes when people want to change something big, other people might try to stop it. That can be a reaction.

More Examples

2

The reforms triggered a conservative reaction.

3

The President's policies were met with an angry reaction from the opposition.

How It's Used

Politics

"The government faced a strong reaction from the public regarding the new tax."

Social

"The reform met with a negative reaction from conservatives."

Tip:It's a *backward* step.

Idioms & expressions

adverse reaction

A harmful or unintended effect caused by a substance, typically a drug or chemical.

"The patient experienced an adverse reaction to the medication."

delayed reaction

A response that occurs some time after the initiating event.

"The news of his promotion was met with a delayed reaction from his colleagues."

knee-jerk reaction

An immediate, unthinking response, often negative or emotional.

"His knee-jerk reaction to criticism was always to get defensive."

From French réaction, from Latin re- (back, again) + actio (action).

The word 'reaction' began to be used in English in the 17th century, initially referring to physical responses, and later extending to social and political contexts.

Memory tip

Think of a chain: an event *acts* on something, and then there is a *reaction*.

Word Origin

Root: reagere

reaktionreacction

Usage

60%Spoken
40%Written