(intransitive) To act in response. / (transitive, now rare) To act or perform a second time; to do over again; to reenact.

(Internet) An emoji used to express a reaction to a post on social media.

simple past tense and past participle of react

present participle of react

Third-person singular simple present indicative form of react

plural of react

A person who responds to a suggestion, stimulation or other influence. / (chemistry, engineering) A structure used to contain chemical or other reactions.

An action or statement in response to a stimulus or other event. / (chemistry) A transformation in which one or more substances is converted into another by combination or decomposition.

(chemistry) A process, typically involving the breaking or making of interatomic bonds, in which one or more substances are changed into others.

(physics) A nuclear reaction in which particles produced by the fission of one atom trigger fissions of other atoms. / (figuratively) A series of events, each one causing or influencing the next.