What does reaction mean?
Reaction means a response to something, but its range extends well beyond the immediate sensation a person experiences when learning unexpected news. It can describe an emotional or political response, such as a public backlash, a bodily response governed by reflex, or the response of one event to another. In chemistry, a reaction is a process involving chemical change, as when two substances combine or a substance breaks down. The word is especially useful because it connects physical, emotional, social, and scientific ideas without requiring the reader to specify the exact kind of response. In general contexts, it often carries a slightly stronger emphasis than response, suggesting that something noteworthy, immediate, or emotionally charged has occurred.
nounA response by a person, organism, chemical system, or other entity to a stimulus, circumstance, or event. The word can also refer to the way in which people respond to a situation, especially emotionally or politically.
- A response to a person, event, situation, or stimulus.
- The emotional or behavioral response of a person or group, especially one that is immediate or pronounced.
- A response or attitude that opposes or resists a proposed action, policy, or development.
- The reverse or opposing response produced by one action or event upon another.
- A change in the chemical composition of a substance, especially one caused by combining or interacting substances.
"Her initial reaction to the unexpected news was one of surprise."
"The proposal met with a strongly negative reaction from residents."
"The metal's reaction to moisture produced a visible coating on its surface."
The plural is used for multiple responses or for the separate responses of different people or groups.
"Public reactions to the decision varied widely."
One word covers an instant human reaction, a bodily reflex, a chemical transformation, and even a political backlash.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does reaction come from?
Reaction entered English in the early 17th century from French réaction, formed from Latin re- and actio, an action or doing. Its underlying verbal root is Latin agere, “to do, act, or drive,” which also underlies English words such as act, action, active, and activity. The prefix re- originally contributed the sense of a return or reverse response, while the word's sense developed to cover responses to stimuli more generally.
Related word forms
How reaction is actually used
In everyday use, reaction often suggests an immediate or emotionally significant response. In chemistry and related sciences, it is the standard term for a process in which substances combine, break down, or undergo transformation; in biology and psychology, it may denote a patterned response to a stimulus.
Easily confused with reaction
A reaction is a general response, whereas a reflex is a rapid, largely involuntary response by the body.
A reaction often emphasizes the manner or emotional character of a response, while a response can be neutral and simply answer or react to something.