What characteristic defines a unilateral contract?

A unilateral contract is defined by a promise in exchange for an act. In this type of contract, one party makes a promise that is contingent upon the performance of a specific act by another party. For instance, a classic example of a unilateral contract is a reward offer, where one party promises to pay a sum of money if someone performs a particular action, like finding and returning a lost pet. The promise is only fulfilled once the act is completed; the performance of that act is what creates the binding nature of the agreement.

This concept distinguishes unilateral contracts from bilateral contracts, where both parties exchange promises. In a bilateral contract, each party is committed to fulfilling their promise and there is a mutual exchange involved, which does not apply in these types of agreements.

The options related to enforceability and mutual consent do not apply specifically to the core characteristic of unilateral contracts. Thus, focusing on the promise in exchange for an act clarifies the unique nature of this contract type.