The meaning of REACTION is the act or process or an instance of reacting. How to use reaction in a sentence.

A chemical reaction is the change that happens when two or more substances are mixed with each other.

A reaction is an action taken in response to something. If you're telling your parents that you want to move out, you'll see by their reaction that they're sad about it.

Usage: Reaction is used to refer both to an instant response (her reaction was one of amazement) and to a considered response in the form of a statement (the Minister gave his reaction to the court's …

Your reaction to something that has happened or something that you have experienced is what you feel, say, or do because of it. Reaction to the visit is mixed.

Reaction definition: A reverse or opposing action.

Jan 20, 2026 · Noun reaction (plural reactions) An action or statement in response to a stimulus or other event.

Reaction is used to refer both to an instant response (her reaction was one of amazement) and to a considered response in the form of a statement (the Minister gave his reaction to the court's decision).

1 day ago · Reaction rates can vary dramatically. For example, the oxidative rusting of iron under Earth's atmosphere is a slow reaction that can take many years, but the combustion of cellulose in a …

For sense development, see reaction. The word meaning "perform again, do a second time" (often written re-act and given full pronunciation of the prefix to distinguish it from react) is attested from …