In legal terms, what is the outcome called when a promise leads a promisee to reasonably rely on it?

The outcome referred to in this context is known as Detrimental Reliance. This legal concept arises when one party makes a promise, and the other party reasonably relies on that promise to their detriment. This reliance typically means that the promisee takes certain actions or refrains from acting based on the promise, leading to potential harm or loss if the promisor fails to fulfill their commitment.

Detrimental reliance establishes a basis for enforcing a promise, especially in cases where the promisee incurs costs or makes decisions believing the promise would be honored. It emphasizes the importance of trust in contractual relationships and acknowledges that parties may suffer negative consequences if promises are not kept. This principle is often invoked in contract law to prevent unjust outcomes where one party relies on the assurances of another.

The other options do not relate directly to the scenario of reliance on a promise. The duty of care refers to a legal obligation to avoid causing harm, adverse possession pertains to acquiring ownership of land through continuous possession, and good faith is a principle related to honesty in transactions but does not specifically encapsulate the idea of reliance on a promise.