Parol evidence rule
The parol evidence rule is a rule in common law jurisdictions limiting the kinds of evidence parties to a contract dispute can introduce when trying to determine the specific terms of a contract and precluding parties who have reduced their agreement to a final written document from later introducing other evidence, such as the content of oral discussions from earlier in the negotiation process, as evidence of a different intent as to the terms of the contract. The rule provides that "extrinsic evidence is inadmissible to vary a written contract".