A rule of evidence providing that a written agreement is the final expression of the agreement of the parties, not to be modified by oral or written negotiations
A common law rule that holds that, if a contract describes itself as being complete and final, any preliminary or informal agreements made prior to or at the same time the contract was made will be ignored when interpreting the contract
An evidence rule of law which says that oral agreements which modify the subject matter of a written contract will be inadmissible in a court of law for the purpose of contradicting what is written in the contract