Английский язык для юристов. Предпринимательское право - стр. 7
A legally complete contract will arise between two parties when all six elements of a contract are present: offer, acceptance, mutual assent, capacity, consideration, and legality. If any one of the six elements is missing, the transaction is not a legally complete contract.
1. An offer is a proposal made by one party to another indicating a willingness to enter into a contract. The person who makes an offer is called the offerer. The person to whom the offer is made is the offeree. Making the offer is actually the first step in creating the contractual relationship between the two parties. The offer must be seriously intended, clear and definite, and communicated to the offeree.
2. In most cases, only the specifically identified offeree has the right to accept an offer. Acceptance means that the offeree agrees to be bound by the terms set up by the offerer in the offer. In many situations, if the offeree changes any of those terms, the acceptance is not really an acceptance but a counteroffer.
3. If a valid offer has been made by the offerer and a valid acceptance has been made by the offeree, then the parties have agreed to the terms, and mutual assent exists between them. Mutual assent is sometimes called a meeting of the minds.
4. Capacity is the legal ability to enter into a contractual relationship. The law has established a general presumption that anyone entering a contractual relationship has the legal capacity to do so.
5. Consideration, i.e. the mutual exchange of benefits and sacrifices, is the thing of value promised to one party in exchange for something else of value promised by the other party. This exchange of valued items or services binds the parties together. If no consideration passes between the parties, then no contract exists.
6. The final element of a binding contract is legality. Parties cannot be allowed to enforce a contract that involves doing something that is illegal. Some illegal contracts involve agreements to commit a crime or to perform a tort. Other activities that are neither crimes nor torts have been made illegal by specific statutes. Among these activities are usurious agreements, wagering agreements, unlicensed agreements, unconscionable agreements, etc.
All contracts are agreements, but not all agreements are contracts. An agreement may or may not be legally enforceable. For example, an agreement to take a friend to a football game would not be legally enforceable because the friend has not given anything in exchange for that promise. To be enforceable, an agreement must conform to the law of contracts.