Which type of contract features only one party's promise?

A unilateral contract features only one party's promise, making it distinct from other contract types. In this arrangement, one party makes a promise that is open for acceptance by the other party's action or performance. A classic example of a unilateral contract is a reward offer. For instance, if someone promises to pay $500 to anyone who finds and returns their lost dog, the promise is binding only once someone completes the action of returning the dog. Until that action is taken, the offeror's promise is not contingent on any reciprocal promise from the other party.

In contrast, a bilateral contract involves mutual promises from both parties, creating obligations on each side. A conditional contract includes obligations that depend on the occurrence of a certain event, while an express contract specifies terms that are clearly stated either verbally or in writing. Understanding these distinctions is key to grasping how different contracts operate in legal contexts.