Contract law is based on the principle expressed in the Latin phrase pacta sunt servanda («Agreements must be respected»).  The Common Law of Contract arose from the meantime defuct writ of assumpsit, which was originally an unlawful act based on trust.  Contract law is covered by the ordinary law of obligations, together with the unlawful act, abusive enrichment and reimbursement.  Drawing in Latin contractus de contrahere, concluding (a relationship or agreement), drawing by com- with, together + trahere An error is a misunderstanding of one or more parts and can be used as a reason for the invalidity of the agreement. The Common Law has identified three types of errors in the treaty: frequent errors, reciprocal errors and unilateral errors. Some arbitration clauses are unenforceable and, in other cases, arbitration proceedings may not be sufficient to resolve a dispute.   If the terms of the contract are uncertain or incomplete, the parties cannot have reached an agreement in the eyes of the law.  An agreement does not constitute a contract and failure to agree on key issues that may include issues such as price or safety can lead to the failure of the entire treaty. . . .