Added 9 October 2026
reaction
/ɹiˈækʃən/ noun
In Latin: reāctiō Wiktionary
noun Definition from WordNet 3.1, Princeton University. Pronunciation from Wiktionary, via Kaikki.org. More about reaction at Wordnik → Where our words come from →
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(chemistry) a process in which one or more substances are changed into others.
there was a chemical reaction of the lime with the ground water
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An idea evoked by some experience.
his reaction to the news was to start planning what to do
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A bodily process occurring due to the effect of some antecedent stimulus or agent.
a bad reaction to the medicine
Origin
Inherited from Middle English reaccion, from Old French reaction, from Latin reāctiō, from the verb reagō, from re- (“again”) + agō (“to act”); more at re-, action; equivalent to react + -ion.
From Wiktionary, via Kaikki.org (CC BY-SA)