English

react

From re- + act.

Formed from re- + act

Proto-Italic *wre- ‘again’

English re-

Proto-Indo-European *h₂eǵ-

…

Latin āctum ‘decree, law’

Latin ācta ‘register of events’

Old French acte

Middle English acte ‘an act’

English act

Today it means

verb To act in response.

Language periods are conventional ranges, not dates for this word.