Definition
To react is to act back — to respond to a stimulus, an event, or a force. The prefix re- ('back') joined to act gives the whole idea: nothing reacts until something first acts upon it. People react to news with joy or alarm; markets react to a single rumour; iron reacts with damp air and slowly begins to erode. A reaction carries no plan of its own — it is shaped entirely by what triggered it, which is why a measured response is so much harder than a reflex.
Examples
- Investors reacted to the rumour before anyone could confirm whether it was true.
- Wise leaders anticipate a crisis instead of waiting to react once the damage is done.
- When the two solutions were mixed, they reacted at once, fizzing and changing colour.
Collocations
react to a situation·react badly·quick to react·react with alarm·an instinct to react
Synonyms
respond·answer·reply·retaliate·counter
Antonyms
ignore·anticipate
Word family
reaction (noun)·reactive (adjective)·reactionary (adjective)·reactor (noun)
In TOEFL & IELTS
React is everyday vocabulary, so in Writing the move is to upgrade around it — 'respond to' or 'address' often read as more academic. Still, react is precise for involuntary or immediate responses (in TOEFL science lectures two chemicals react; in IELTS, public opinion reacts). Mind the preposition — you react TO something — and the noun reaction, which collocates with provoke, trigger, and chain.