chapter thirteen Tools A B parol evidence rule rule under which a written contract cannot be changes by prior oral or written agreements express contract contract in which the agreement of the parties is spoken or written formal contract writen contract that must be in a special form to be enforced executed contract contract that has been fully performed simple contract any contract that is not a formal contract implied contract contract in which intent of the parties is shown by conduct or circumstances quasi contract obligation that is enforced as if it were a contract in order to prevent unjust enrichment of one party statute of frauds law stating that certain agreements are not enforceable unless they are in writing and are signed by the party against whom the contract to be enforced executory contract contract that has not been fully performed contract of adhesion contract in which the more powerful party dictates all the important terms