What type of contract is formed when only one party is legally bound?

A unilateral contract is formed when only one party is legally bound to fulfill their obligations under the contract. In this type of contract, one party makes a promise in exchange for a specific action or performance by the other party. For example, if someone offers a reward for the return of a lost pet, the person offering the reward is obligated to pay it upon the successful return of the pet, while the person who finds the pet is not legally required to do anything—hence only one party has a legal obligation.

In contrast, a bilateral contract involves mutual obligations where both parties make promises to each other, thereby creating reciprocal duties. A personal contract generally refers to an agreement that is tailored to specific individuals, while an implied contract arises from the actions or circumstances of the parties rather than from a written or spoken agreement.

Thus, the definition and characteristics of a unilateral contract clearly demonstrate why it is the type of contract where only one party is legally bound.