Consideration

The term "consideration" has three meanings or usages:
 * 약인(約因): NOW, THEREFORE, in consideration of the mutual covenants and agreements hereinafter set forth, the parties hereto agree as follows. 이에 다음에 정하는 상호간의 서약과 약속을 약인으로 하여 계약당사자는 아래와 같이 합의한다.
 * 대가(對價): In an M&A agreement, Consideration means the price of the target company. M&A 계약에 있어서는 인수대상 기업의 가치를 의미한다.
 * 고려(考慮): Party A shall take the price, quantity and other factors into considerartion. 사전적 의미 그대로 당사자 A는 가격, 수량 그 밖의 요소를 고려해야 한다는 뜻이다.

Generally speaking, in common law countries, consideration is required for the formation of a contract, but in civil law countries, it is not required.

In Common law
Consideration is the concept of legal value in connection with contracts. It is anything of value promised to another when making a contract. It can take the form of money, physical objects, services, promised actions, abstinence from a future action, and much more.

Consideration to create a legally enforceable contract entails a detriment to the promisee OR a benefit to the promisor. Under the notion of "pre-existing duties", if either the promisor or the promisee already had a legal obligation to render such payment, it cannot be seen as consideration in the legal sense.

So a contract is not enforceable unless it has consideration, but a trust does not need consideration in order to be enforceable.

In common law, it is a prerequisite that both parties offer consideration before a contract can be thought of as binding. The doctrine of consideration is irrelevant in many jurisdictions, although contemporary commercial litigant relations have held the relationship between a promise and a deed is a reflection of the nature of contractual considerations.

If there is no element of consideration found, there is thus no contract formed. However, even if a court decides there is no contract, there might be a possible recovery under quantum meruit (sometimes referred to as a quasi-contract) or promissory estoppel.

General usage
In common law countries, consideration is used as follows:
 * valuable consideration: 법률상의 유가(有價)약인
 * executed consideration: 기행(旣行)약인
 * executory consideration: 미이행(未履行)약인
 * pecuniary consideration: 금전상의 약인
 * moral consideration: 도덕상의 약인
 * additional consideration: 추가적인 약인
 * failure of consideration: 약인의 실효, 멸실
 * naked agreement: 약인이 없는 계약