to reply or react to something

उत्तर देना

English Usage: She did not respond to the email.

Hindi Usage: उसने ईमेल का उत्तर नहीं दिया।

a reaction to something

प्रतिक्रिया

English Usage: Her response to the question was unexpected.

Hindi Usage: उसके सवाल पर प्रतिक्रिया अप्रत्याशित थी।

people who respond to a situation, often in emergencies

प्रतिक्रिया देने वाले

English Usage: The responders arrived at the scene quickly.

Hindi Usage: प्रतिक्रिया देने वाले जल्दी से मौके पर पहुंच गए।