What type of contract is characterized by only one party making a promise that is enforceable by law?

A contract characterized by only one party making a promise that is enforceable by law is known as a unilateral contract. In this arrangement, one party (the promisor) makes a promise that the other party (the promisee) can accept by performing a certain action. A common example of a unilateral contract is a reward offer; for instance, if someone promises to pay a reward for the return of lost property, only the person making the promise is legally bound to fulfill that promise. The return of the property by another party completes the contract but does not impose any reciprocal obligations on the promisee until the action is taken.

This principle distinguishes unilateral contracts from mutual (or bilateral) contracts, where both parties make promises to each other, creating mutual obligations. Such clarity in definitions is crucial for understanding contract law as it pertains to various agreements and their enforceability in legal contexts.