Civil Code (Cap. 16), article 962

962. (1) When each of the parties u ndertakes an obligation, the contract is te rmed onerous. (2) When one of the parties gratuitously procures an advantage to the other, the contract is termed gratuitous. commutative, 963. A contract is commutative, when each party binds himself to give or to do a thing which i s considered as the equivalent of that which is given to or done for him. aleatory. 964. When the advantage or loss, whether to both parties or one of them, depends on an uncertain event, the contract is aleator y. Rules governing contracts.