In common law legal systems, a contract (or informally known as an agreement in some jurisdictions) is an agreement having a lawful object entered into voluntarily by two or more parties, each of whom intends to create one or more legal obligations between them. The elements of a contract are "offer" and "acceptance" by "competent persons" having legal capacity who exchange "consideration" to create "mutuality of obligation."Proof of some or all of these elements may be done in writing, though contracts may be made entirely orally or by conduct. The remedy for breach of contract can be "damages" in the form of compensation of money or specific performance enforced through an injunction. Both of these remedies award the party at loss the "benefit of the bargain" or expectation damages, which are greater than mere reliance damages, as in promissory estoppel. The parties may be natural persons or juristic persons. A contract is a legally enforceable promise or undertaking that something will or will not occur. The word promise can be used as a legal synonym for contract, although care is required as a promise may not have the full standing of a contract, as when it is an agreement without consideration.Contract law varies greatly from one jurisdiction to another, including differences in common law compared to civil law, the impact of received law, particularly from England in common law countries, and of law codified in regional legislation. Regarding Australian Contract Law for example, there are 40 relevant acts which impact on the interpretation of contract at the Commonwealth (Federal / national) level, and an additional 26 acts at the level of the state of NSW. In addition there are 6 international instruments or conventions which are applicable for international dealings, such as the United Nations Convention on Contracts for the International Sale of Goods.