Which type of contract is dependent on the occurrence of an uncertain event?

An aleatory contract is one that is contingent upon the occurrence of an uncertain event, which means that the obligations of one or both parties are triggered by a specific event that may or may not happen. In insurance contracts, for example, the insurer's obligation to pay a claim is dependent on the occurrence of a loss, which is uncertain until it happens. This relationship exemplifies the core principle of aleatory contracts: the exchange of values may not be equal, as one party might receive a benefit only if a certain event occurs.

In contrast, fixed contracts involve obligations that are predetermined and do not hinge on uncertain events; the terms are rigid, and performance is expected regardless of external conditions. Conditional contracts, while also dependent on certain events, typically outline conditions under which performance is required but do not capture the essence of how the exchange is structured around risk and uncertainty like aleatory contracts do. Permanent contracts suggest a continuity without conditions that hinge on uncertain events, making them irrelevant in this context. Thus, the classification of an aleatory contract aligns perfectly with the definition provided in the question.