Parol evidence rule
（重定向自Parol evidence）
The parol evidence rule is a substantive common law rule in contract cases that prevents a party to a written contract from presenting extrinsic evidence that discloses an ambiguity and clarifies it or adds to the written terms of the contract that appears to be whole. The term of art parol means "oral" and comes from Anglo-French, Anglo-Norman, or Legal French.