What type of contract binds only one party to a legally enforceable promise?

A unilateral contract is a type of contract that binds only one party to fulfill a legally enforceable promise. In this form of contract, one party makes a promise in exchange for an act by another party. For example, if someone promises to pay a reward for finding a lost pet, only the person offering the reward is legally bound to pay once the act of finding the pet is completed. The other party (the one searching for the pet) is not bound to perform any action; they can choose to do so or not.

In many contexts, unilateral contracts are significant because they emphasize the importance of conditional performance rather than reciprocal obligations, which are typical in bilateral contracts where both parties commit to perform specific duties.

The other concepts do not align with the definition of a contractual obligation that binds only one party. An aleatory contract involves an exchange that is contingent on a certain event, typically relating to chance. A personal contract typically involves obligations stemming from personal relationships and may require mutual commitments. A conditional contract obligates one or both parties only under specific conditions which may not apply to the scenario where only one party is bound by a promise.