- According to the BarBri Contracts Review, "a contract is a promise or set of promises, for breach of which the law gives a remedy, or the performance of which the law in some way recognizes as a duty." A valid contract consists of an offer, acceptance of that offer, and "consideration" (a bargained-for benefit between the parties). Consideration isn't necessary if one party relies on the other's promise and suffers a detriment as a result ("detrimental reliance").
- The validity of a contract is not affected by whether the contract was formed orally or in writing. Written contracts are easier to enforce after-the-fact. Some jurisdictions also have a shorter statute of limitations for the enforcement of an oral contract as opposed to a written contract.
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Contracts are classified whether they are "unilateral" or "bilateral" contracts.
A bilateral contract contains an exchange of promises in which each party has both a right and a duty. This covers most contracts. An example would be that Bill hires Ted to paint his room in exchange for $50.
In a unilateral contract only the offerer has a duty. The offeree has no duty to perform, but has a right to the contract once he performs. For example, Bill offers a $100 reward for the return of his lost guitar. -
Contracts are also classified based on how they are created.
An express contract is formed by stating the terms of the contract, whether orally or in writing.
An implied Contract is formed without written terms, but inferred by conduct, typically by partial performance.
A quasi-contract isn't technically a contract, but a legal construct that will sometimes be used by judges to allow a plaintiff to seek restitution where no formal contract existed, and prevent a defendant from being unjustly enriched. -
In a contract of adhesion, an offeror's standard form contract does not allow the offeree to negotiate the terms. This often (but not always) implies unequal bargaining positions between the parties, i.e., "take it or leave it."
In an output contract, according to law.com, "a producer agrees to sell its entire production to the buyer, who in turn agrees to purchase the entire output."
In a requirements contract, the buyer agrees to fill his needs for a product from one supplier and the supplier agrees to meet all those needs (within reason).
