What term is used for a contract that involves an unequal transfer of value based on a certain event?

The term "aleatory" refers to a type of contract in which the obligations of one or both parties are contingent upon an uncertain event. This means that there is an unequal transfer of value, as one party may receive a large benefit from the contract if the event occurs, while the other party's obligation may remain relatively small or even negligible.

In insurance, for example, the premium paid by the insured is often small compared to the potential payout that the insurer could be obligated to make if a covered event occurs, such as a loss or damage. This asymmetrical value transfer is a fundamental aspect of aleatory contracts, highlighting how the contract's performance relies on uncertain future events.

The other terms have specific meanings in the context of contracts but do not accurately capture the essence of an unequal value exchange based on a particular event. A reciprocal contract implies mutual exchange of values, making it different from the aleatory nature. Conditional contracts involve obligations that arise based on specific conditions, but they do not inherently emphasize the unequal value aspect. Unilateral contracts are those in which only one party makes a promise or performs, and while there may be unequal value, it does not necessarily hinge on the uncertainties of an event like those found in aleatory contracts.