In French law. Contracts are of the following varieties: (1) Bilateral, or synallagiiiatiqne, where each party is bound to the other to do what is just and proper; or (2) unilateral, where the one side only is bound; or (3) committal if. where one does to the other something which is supposed to be an equivalent for what the other does to him; or (4) aleatoirc, where the consideration for the act of the one is a mere chance; or (5) cuntrat de bienfuisance, where the one party procures to the other a purely gratuitous benefit; or (0) contrat d titre oncreiw, where each party is bound under some duty to the other. Brown.