an action performed in response to a stimulus

a response or reply

उत्तर

English Usage: He had a quick reaction to her question.

Hindi Usage: उसके सवाल पर उसका उत्तर जल्दी था।

to respond or behave in a particular way when something happens

to respond to a chemical or physical stimulus

chemical या भौतिक उत्तेजना पर प्रतिक्रिया करना

English Usage: The substances will react when mixed together.

Hindi Usage: पदार्थ जब मिलाए जाते हैं तो प्रतिक्रिया करेंगे।