What is the term for a contract in which the exchange of value is unequal?

The term for a contract in which the exchange of value is unequal is referred to as "aleatory." In the context of insurance, this means that one party may pay premiums, but the benefit they receive in the form of a payout may far exceed the amount contributed, depending on the occurrence of the insured event.

For example, in a life insurance policy, the policyholder pays regular premiums, and if the insured individual passes away, the insurance company pays out a significantly larger sum. This creates an element of chance; the amount given by the insurer is contingent upon an event that may or may not happen, making the exchange unequal at the outset. This characteristic is fundamental to insurance contracts and distinguishes them from many other types of agreements, where the values exchanged are typically more balanced.

The other terms do not specifically refer to this unequal exchange aspect of contracts. "Conditional" refers to the fact that certain obligations or benefits arise only under specified conditions. "Legal" simply means that the contract is enforceable under law, and "unilateral" denotes a contract where only one party makes a promise, with the other party acting upon that promise, without necessarily addressing the value exchanged.