/ˈpærəl ˈɛvɪdəns ruːl/ – Phrase
Definition: Nguyên tắc bằng chứng bằng lời nói.
A more throughout explanation: the rule that the terms of a written contract cannot be altered by evidence of any prior written or oral agreement
Example: To avoid the parol evidence rule make sure that all the terms you want in the contract are actually stated in the contract.