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# reaction

noun (a reaction, reactions)

«reaction» in the English dictionary: everyday — its meanings, how the lessons use it, and examples, each with its tree on Mova.

## Everyday

1. What someone says, does or feels because of something that has happened: her reaction to the news was a big smile. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#m1)
2. In science, a chemical reaction is when substances change into new substances, like vinegar and bicarbonate of soda fizzing. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#m2)
3. An allergic reaction is when the body responds badly to something, such as nuts or a bee sting. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#m3)
4. How quickly you respond: fast reactions. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#m4)
5. In forces, a reaction is the push back in the opposite direction. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#m5)
6. A reaction can also be a movement that turns back against a change or an earlier way of doing things. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#m6)

### In the lessons

In science, signs of a chemical reaction include fizzing (a gas), a colour change, heat or light, or a new solid forming; burning and rusting are reactions that cannot be undone. In health, an allergic reaction can cause a rash, swelling or trouble breathing; a severe one (anaphylaxis) is an emergency — call for help and an adult may use an adrenaline pen. In sport and games, quick reactions help you catch a ball. In stories, a character's reaction shows how they feel. Phrases: "chemical reaction", "allergic reaction", "a quick reaction", "reaction time", "chain reaction".

### Examples

- What was your reaction when you saw the surprise? [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x1)
- Mixing vinegar and baking soda causes a fizzy reaction. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x2)
- She had an allergic reaction to the peanuts. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x3)
- Rusting is a slow chemical reaction. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x4)
- Goalkeepers need fast reactions. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x5)
- His reaction was to burst out laughing. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x6)
- We measured our reaction times with a falling ruler. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x7)
- The fizzing told us a reaction was happening. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x8)
- When the Hindu reaction against Buddhism came, the Brahmins adapted these, with the omission of Buddha as the central figure. [tree →](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/#x9)

### Note

Countable: a reaction, reactions. Verb: react; adjective: reactive. Melting and dissolving are usually changes, not chemical reactions, because no new substance is made. Any sign of a bad allergic reaction (swelling of lips or tongue, wheezing) needs an adult and emergency help at once.

## On Mova

- [Trees and pragmatics of «reaction» in the school dictionary](https://mova.elamur.ai/free/en/corpora/dictionaries/school/R/reaction/): every meaning and example parsed by Mova, with its dependency tree and frames.
- [«reaction» in the school dictionary](https://mova.elamur.ai/free/en/dictionaries/school/w/reaction.html) on Mova free.