# reaction

Pronunciation: say "ree-AK-shuhn" /ɹiˈækʃən/

## Noun

1. What someone does, says, or feels in answer to something that has happened.
   - Simple: What you do, say, or feel because something has happened.
   - _His immediate reaction to the criticism was to defend himself._
   - _Public reactions to the new policy ranged from praise to outrage._
2. A process in which one or more substances are changed into one or more new substances.
   - Simple: A change in which one or more substances turn into new substances.
   - _The reaction between hydrogen and oxygen produces water._
   - _Chemists slowed the reaction by lowering the temperature._
3. An instance of the body responding badly to a drug, food, or other substance, causing harm or discomfort.
   - Simple: A bad or harmful effect on your body caused by a medicine, food or other substance.
   - _The patient suffered an allergic reaction to the contrast dye used in her scan._
   - _Nurses watched for any reaction during the first hour after the vaccine was given._
4. A person's capacity to move or act fast in physical response to something sudden; used in the plural.
   - Simple: Your ability to move fast when something suddenly happens.
   - _Quick reactions saved the cyclist when a car door swung open right in front of her._
   - _Years of table tennis had given him lightning reactions._
5. An icon or emoji added to a posted message to express how the user feels about it.
   - Simple: A small icon or emoji you add to a message to show how you feel about it.
   - _He tapped a thumbs-up reaction on the group message._
   - _Within an hour the post had hundreds of reactions, mostly hearts and laughing faces, but only a few comments._
6. The force of equal size and opposite direction that a body exerts in return whenever another force is applied to it.
   - Simple: The push or pull an object gives back, just as strong as the force on it but in the opposite direction.
   - _As she presses down on the floor, the reaction of the floor pushes up on her feet with equal force._
   - _A rifle recoils because of the reaction to the force that drives the bullet down the barrel._
7. Politics aimed at undoing recent changes and restoring an earlier order, or a time when those politics or ideas regain strength or prevail.
   - Simple: Politics that tries to undo recent changes and bring back an older system, or a time when those ideas grow powerful.
   - _The decade after the uprising was a period of deep reaction._
   - _Historians describe the era as one of political reaction against the earlier reforms._

## Origin

This word came through Middle English 'reaccion' from Latin 'reāctiō', which comes from the verb 'reagō', formed from 're-' ('again') plus 'agō' ('to act'); it is equivalent to 'react' plus '-ion'.

Source: DictionaryAI, https://dictionaryai.com/define/reaction (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).