Which term describes the legal process that prevents a party to a contract from asserting a right after waiving it?

The term that describes the legal process preventing a party to a contract from asserting a right after waiving it is estoppel. Estoppel acts as a safeguard to ensure fairness and prevent a party from going back on their word or actions that led another party to reasonably rely on their initial waiver of that right.

In contract law, if one party indicates that they will not enforce a right or obligation, and the other party acts on that reliance, the party that initially waived the right cannot later claim that right again. This prevents unjust outcomes and promotes trust in contractual agreements.

In contrast, nullification refers to the act of cancelling or invalidating a contract or agreement, while abandonment typically involves relinquishing a right or interest in an agreement without intention to return. Exemption, on the other hand, often refers to being free from something that is usually mandatory or obligatory. Thus, estoppel specifically addresses the issue of enforcing rights after they have been waived, making it the correct term in this context.