An agreement is an expansionary approach that includes any agreement or understanding between two or more parties on their rights and obligations with respect to the other. Such informal agreements often take the form of gentlemen`s agreements, in which compliance with the terms of the agreement is based on the honour of the parties concerned and not on external means of implementation. In the United States, an unusual type of unenforceable contract is a personal employment contract to work as a spy or secret agent. This is due to the fact that the secrecy of the contract itself is a condition of the contract (in order to preserve a plausible negation). If the spy then sues the government over issues such as salary or social benefits, the spy has breached the contract by revealing its existence. It is therefore unenforceable for this reason, as is public policy of maintaining national security (since an angry agent could attempt to reveal all the secrets of the government during his pursuit).  Other types of non-binding employment contracts include contracts that commit to working for less than the minimum wage and the loss of workers` right to compensation in cases where work compensation is due. In colonial times, the concept of consideration was exported to many common law countries, but it is unknown in Scotland and civil courts.  Roman legal systems do not require or recognize any consideration, and some commentators have proposed abandoning the counterpart and replacing it as the basis for treaties.  However, legislation, not the development of justice, has been presented as the only way to eliminate this entrenched doctrine from the common law. Lord Justice Denning said: "The doctrine of consideration is too well entrenched to be overturned by a side wind."  In the United States, the focus has been on the negotiation process, as hamer v. Sidway (1891) shows.
Contracts are widespread in commercial law and are the legal basis for transactions worldwide. The most common examples are contracts for the sale of services and goods (wholesale and retail trade), construction contracts, transport contracts, software licenses, employment contracts, insurance policies, sale or lease of land and various other uses. While trade and exchange rules pre-existed since ancient times, modern contract laws in the West have been understandable since the Industrial Revolution (from 1750), when more and more people worked in factories for a cash wage. In particular, the growing strength of the British economy and the adaptability and flexibility of English common law have led to a rapid evolution of English contract law. The colonies of the British Empire (including the United States and the Dominions) would take over metropolitan law. In the twentieth century, the growth of export trade led countries to adopt international agreements such as the Visby Hague Rules and the United Nations Convention on Contracts for the International Purchase of Goods in order to promote uniform rules. . .