Synallagmatic contract

In civil law systems, a synallagmatic contract is a contract in which each party is bound to provide something to the other party. Its name comes from the Ancient Greek synallagma, meaning mutual agreement, and examples include contracts of sale, of service and of hiring. In common law jurisdictions it is roughly the equivalent of a bilateral contract. It may be contrasted with a gift, because a gift is not a relationship of contract, and with a unilateral contract, in which only one party makes an enforceable promise. Commenting on the case of Hong Kong Fir Shipping Co Ltd v Kawasaki Kisen Kaisha Ltd, Lord Diplock observed that every synallagmatic contract contains the seeds of a problem, namely in what event a party will be relieved of his undertaking to do that which he has agreed to do but has not yet done.