A small piece of metal that opens a lock.

Something that is essential for understanding or achieving something.

किसी चीज़ को समझने या प्राप्त करने के लिए आवश्यक कुछ

English Usage: Communication is the key to a successful relationship.

Hindi Usage: संचार एक सफल रिश्ते की कुंजी है।

Of crucial importance.

महत्वपूर्णता का

English Usage: He played a key role in the negotiations.

Hindi Usage: उसने बातचीत में महत्वपूर्ण भूमिका निभाई।