A more thorough explanation:

Definition: Dejeration is the act of making a solemn promise or oath.

Examples:

• When the president takes the oath of office, he is making a dejeration to uphold the Constitution.
• During a wedding ceremony, the couple makes a dejeration to love and cherish each other for the rest of their lives.

The examples show how dejeration involves making a serious promise or commitment. It is a formal declaration that someone is making, often in front of witnesses or a higher authority.