An agreement in which only one party promises to perform without receiving a reciprocal promise is called what?

A unilateral contract is defined as an agreement where one party makes a promise to perform a certain action without receiving any reciprocal promise from the other party. In this type of contract, only the offeror is obligated to fulfill their promise, while the other party is not bound to perform any duty or obligation unless they choose to accept the offer through their actions.

For example, a common scenario illustrating a unilateral contract is when a person offers a reward for the return of a lost item. The person making the offer is promising to pay a specific amount of money if someone finds and returns the item, but the individual who finds the item is not required to take any action in response to the offer.

In contrast, a bilateral contract involves a mutual exchange of promises, where both parties are obligated to perform certain duties. A joint venture agreement typically involves two or more parties working together for a common business goal and includes reciprocal commitments. An option agreement grants one party the exclusive right to make a transaction within a specified time frame, but it still involves an element of mutual agreement.

Thus, the defining characteristic that distinguishes a unilateral contract is the one-sided promise, making it the correct answer in this context.