What refers to a promise that may not require consideration to be enforceable?

A unilateral contract is a type of agreement where one party makes a promise in exchange for an act or performance by another party, and it does not require consideration from the other party to be enforceable. In essence, when one party makes a promise that someone else can accept by performing a certain task, the completion of that task constitutes acceptance of the offer, and the promise becomes enforceable.

For example, if someone offers a reward for the return of a lost pet, the offeror is bound to pay the reward once the pet is returned. The person who finds and returns the pet does not have to provide any additional consideration beyond the act of returning the pet to accept the offer.

This distinguishes unilateral contracts from bilateral contracts, where both parties exchange promises, and consideration is typically required from both sides to create enforceability. Implied contracts and express contracts also follow different principles related to the necessity of consideration. Thus, understanding these distinctions highlights the unique nature of unilateral contracts and their enforceability without the requirement of consideration.