What type of contract is characterized by an enforceable promise from only one party?

A unilateral contract is defined as a type of agreement in which one party makes a promise that the other party can only accept by performing a specific action. In this scenario, the promise from one party stands alone and is enforceable once the other party completes the required act or duty. A classic example of this is a reward contract, where one person promises to pay a reward to anyone who finds and returns their lost dog. The promise is enforceable once the dog is returned, but until that action occurs, there is no obligation on the part of the person who might potentially gather the reward.

This scenario distinguishes unilateral contracts from other types like bilateral contracts, where both parties exchange mutual promises, or mutual contracts, which also require agreements from both sides. Conditional contracts are based on the occurrence of specific events, but they typically involve obligations from both parties. Hence, the defining characteristic of a unilateral contract is its dependence on the performance of a specific action by only one party for it to be enforceable.