reactions

IPA/riˈæk.ʃən/
KK[riˈækʃənz]IPA/riˈæk.ʃən/

reactions — noun

  • reactionssingular
  • reactionsesplural

1. what you do, feel, or say because something has happened, or as a result of a si

1.nounB1
Definition

what you do, feel, or say because something has happened, or as a result of a situation or event

Example

Selim's first reaction to the news was a long, silent pause.

reaction + to + noun (news)

The audience reaction to the final scene was loud applause.

Common collocations
  • strong reaction
  • mixed reaction
  • immediate reaction
  • emotional reaction
  • reaction to
Synonyms
  • response

    more neutral and formal than reaction

  • reply

    used only for spoken or written answers, not feelings

  • feedback

    opinions about a product, service, or performance

Grammar Patterns

reaction + to + noun

Usage Note

Often followed by 'to' to show what caused the response. The adjective before 'reaction' (e.g. strong, mixed, immediate) shows the type of response.

Common Mistakes

My reaction of the movie was good.
My reaction to the movie was positive.
use 'to', not 'of', after 'reaction'.

2. the speed at which someone notices something and responds, especially in a physi

2.nounB2
Definition

the speed at which someone notices something and responds, especially in a physical or urgent situation

Example

A racing driver needs incredibly quick reactions to avoid crashes.

quick reactions — adjective + plural noun

Megan's reactions slowed down after she had been studying for six hours straight.

Common collocations
  • quick reactions
  • slow reactions
  • lightning reactions
  • good reactions
  • poor reactions
Synonyms
  • reflexes

    more specific — refers to automatic physical responses

  • alertness

    focuses on being awake and ready, not speed of response

Grammar Patterns

possessive + reactions

Usage Note

Almost always used in the plural form (reactions) or as an uncountable noun (reaction time). Common with adjectives like quick, fast, slow, poor, lightning.

Common Mistakes

He has good reaction.
He has good reactions.' or 'He has a good reaction time.
for physical speed of response, use the plural.

3. a way of behaving or thinking that deliberately goes against what is usual, expe

3.nounB2
Definition

a way of behaving or thinking that deliberately goes against what is usual, expected, or required by society or authority

Example

The punk fashion movement was a reaction against the conservative styles of the 1970s.

reaction + against + noun — the target of opposition

Sofie dyed her hair bright pink as a reaction against her school's strict uniform policy.

Common collocations
  • reaction against
  • backlash
  • rebellion
  • pushback
Synonyms
  • backlash

    stronger and more hostile; a sudden negative reaction

  • rebellion

    more active and organized — involves defying authority openly

  • pushback

    informal, often used in business or politics

Antonyms

Grammar Patterns

reaction + against + noun

Common Mistakes

His reaction to the government was to join the protest.
His reaction against government policies led him to join the protest.
use 'against', not 'to', when describing opposition.

4. a physical response by the body, usually unpleasant, caused by something a perso

4.nounB2
Definition

a physical response by the body, usually unpleasant, caused by something a person eats, touches, or takes as medicine

Example

When three-year-old Liam ate peanut butter for the first time, he got a red skin reaction around his mouth.

skin reaction — type of reaction + location on body

Élise had a bad reaction to the antibiotic and broke out in red spots.

reaction + to + noun (cause of reaction)

Common collocations
  • allergic reaction
  • bad reaction
  • skin reaction
  • reaction to
Synonyms
  • allergy

    a long-term condition, not the event itself

  • side effect

    specifically for reactions to drugs, not food

Grammar Patterns

allergic reaction + to + noun

Usage Note

Common in medical contexts. 'Allergic reaction' is the most frequent collocation. Used with 'to' to specify the trigger (food, drug, insect sting, etc.). Can be mild (rash, sneezing) or severe (anaphylaxis).

Common Mistakes

She had reaction to the medicine.
She had a reaction to the medicine.
'reaction' in this sense is countable and needs an article.

5. the way materials mix, separate, or change into different substances — for examp

5.nounB2
Definition

the way materials mix, separate, or change into different substances — for example, when baking soda and vinegar fizz together

Example

In science class, the students mixed baking soda and vinegar to observe a chemical reaction.

chemical reaction — noun phrase used with 'observe'

When iron rusts, a slow chemical reaction between the metal and oxygen is taking place.

chemical reaction + between + noun + and + noun

Common collocations
  • chemical reaction
  • produce a reaction
  • cause a reaction
  • reaction between
Synonyms
  • chemical process

    broader term — includes reactions and other changes

  • change

    too general; use only when context is already clear

Grammar Patterns

chemical reaction + between + plural noun

Usage Note

This meaning belongs to the domain of chemistry and science. 'Chemical reaction' is the standard full term. Can be described as fast or slow, and as producing or consuming heat (exothermic / endothermic).

Common Mistakes

The chemical reaction between the two elements created water.
The chemical reaction between hydrogen and oxygen produces water.
use 'produces' or 'releases', not 'creates', for standard chemistry descriptions.

6. a determined opposition to any reform in society or government, often with a wis

6.nounC1
Definition

a determined opposition to any reform in society or government, often with a wish to return to earlier values or systems

Example

The rise of political reaction in 1930s Europe led to stricter controls on what writers could publish.

uncountable use — 'reaction' as an abstract political force

Historians describe the post-war decades as a period of reaction, when every proposal for social reform was met with suspicion.

Common collocations
  • period of reaction
  • force of reaction
  • rise of reaction
Synonyms
  • conservatism

    broader and less extreme; not always opposed to all change

  • traditionalism

    focuses on preserving customs rather than opposing political change

Antonyms
  • progressivism

    belief in gradual social improvement through change

  • reform

    the act of making changes to improve a system

Usage Note

Uncountable in this sense; do not use 'a reaction' when describing the political stance. Often used in history and political science writing. The adjective 'reactionary' describes a person who holds these views.

Common Mistakes

The prime minister is a reaction.
The prime minister is a reactionary.
'reaction' is the concept; 'reactionary' is the person who supports it.

7. the backward push of equal strength that arises whenever one object presses agai

7.nounC1
Definition

the backward push of equal strength that arises whenever one object presses against another object, as described by Newton's third law of motion

Example

When you push against a wall, the wall exerts an equal reaction force back on your hand.

reaction force — technical term in physics

When the rocket engine ignites, the reaction from the burning fuel pushes the rocket upward in the opposite direction.

Common collocations
  • action and reaction
  • reaction force
  • equal and opposite reaction

Grammar Patterns

action + and + reaction

Usage Note

Almost always appears in physics contexts. The phrase 'action and reaction' is a fixed expression from Newton's third law. 'Reaction force' is a common compound noun in engineering and mechanics.

Common Mistakes

For every action, there is a reaction.
For every action, there is an equal and opposite reaction.
the phrase 'equal and opposite' is part of the standard statement of Newton's third law.

Word family

Synonym discussion

Sense: noun/1

Reaction, response, reply, and feedback all describe something said or done after an event, but they differ in scope and use. Reaction is the broadest — it includes feelings, behaviour, and physical effects, often suggesting an automatic or emotional quality ('Her reaction to the news was tears'). Response is more deliberate and measured, often used in formal or analytical contexts ('The government's response to the crisis involved new policies'). Reply is restricted to words — a spoken or written answer ('I sent a reply to her email'). Feedback is specific to opinions about a product, performance, or idea, typically given to help someone improve ('The teacher gave feedback on the essay'). In everyday use, reaction and response overlap most, but reaction leans toward the instinctive while response suggests thought.

response ↗reply ↗feedback ↗reaction ↗

Common collocations

Nouns

  • chain reaction
  • knee-jerk reaction
  • allergic reaction
  • chemical reaction
  • adverse reaction

Adverbs

Phrases

  • in reaction to
  • as a reaction against
  • cause a reaction
  • provoke a reaction

Prepositions

Etymology

LatinFrenchEnglish

Reaction comes from the Latin 'reactio', formed from 're-' (back, again) and 'actio' (doing, driving). The word entered English in the 1600s through scientific writing, first describing how one substance affects another and later expanding to cover emotional responses, political opposition, and physical forces. The modern plural form 'reactions' became common in the 1800s to describe quick reflexes and chemical processes.

First known use

1585

1585, in the meaning defined at sense 1a