A contract where one party promises to act based on the other party's performance is known as a?

A contract where one party promises to act based on the other party's performance is categorized as a unilateral contract. In this type of agreement, one party makes a promise that is contingent upon the other party performing a specific act or fulfilling a certain condition. This means that the second party does not need to make a promise in return; instead, their performance of the requested act constitutes acceptance of the offer.

An example of a unilateral contract is a reward offer: if someone posts a reward for finding a lost pet, the person who finds and returns the pet does so in exchange for the reward. Here, the reward is only offered after the specific performance of returning the pet is completed.

The other types of contracts mentioned—unenforceable, void, and bilateral—have different characteristics that do not fit the scenario described. An unenforceable contract is one that cannot be enforced in a court of law for some reason, a void contract is one that has no legal effect from the beginning, and a bilateral contract involves two parties exchanging promises to perform. Understanding these distinctions helps clarify why the unilateral contract is the correct answer in this context.