To assert or insist emphatically that something is true, often in the face of doubt or disbelief.

जोर देकर कहना

English Usage: He swears blind that he finished the project on time.

Hindi Usage: वह जोर देकर कहता है कि उसने प्रोजेक्ट समय पर पूरा किया।

An oath or a promise, particularly of one’s integrity or intention.

शपथ

English Usage: He took a swear to uphold the law.

Hindi Usage: उसने कानून का पालन करने की शपथ ली।