“对价”或“约因”是合同中经常可以见到的词，对应的英文表达为“consideration”。

consideration是英美合同法中至关重要的一个核心概念,通常被翻译为“对价”或“约因”。此外，常见的组合有valuable consideration(有值对价)、good consideration( 道德对价)意思是“出于亲属之间的爱、感、情或道义责任上的考虑,而承诺提供利益或移交财产,受益人不得请求强制执行承诺.....”

一般而言good consideration 和valuable consideration 的区别就在于前者无真正的对价支持,后者指一方付出有价值的代价,能换取对方的承诺或作为。前者不应被视为真正的对价。因此,无真正对价支持的合同也就没有强制执行力。

简言之,“对价”就是合同双方交换有价值东西的代价。“对价”是相对应的代价,通俗地说，就是相当或对等的代价。

例1 If mutuality of consideration is not present, there is no contract.

[参考译文]如果没有相互的对价,那么就没有合同。

此外这句话也可以这么说: No consideration， no contract. (合同无对价不成立。)

例2 Consideration must be of value ( at least to the parties), and is exchanged for the performance or promise of performance by the other party ( such performance itself is consideration).

[参考译文] 对价必须(至少对合同双方)是有价值的,并且对价的交换必须通过另一方履行或承诺履行(这样的履行本身就是对价)。

例3 A gift is a fairly common means of acquiring and transferring ownership of real and personal property. A gift is essentially a voluntary transfer of property ownership for which no considera-tion.

[参考译文] 赠与是一种相当普遍的获得和转移动产及不动产所有权的方式。从本质上来说,赠与是一种自愿转移财产所有权行为,没有与之相应的对价。

例4 If there has been an offer and an acceptance, a contract is normally created. A promise that is unsupported by considera-tion, however, even if accepted, does not create a contract.

[参考译文] - -般情况下,若要约与承诺已经存在,则合同正式成立。但没有对价支持的允诺即使已被接受,合同也不能成立。

例5 There must be consideration to support a contractual claim. Consideration is defined as bargained for exchange.

[参考译文]合同的权利必须有对价支持。对价被界定为是允诺的交换。

以上参考《法律英语核心词汇》（屈文生）

PS：释义

《元照英美法词典》释义

good consideration ①道德对价; 情感对价。指纯然基 于爱或情感而产生的对价，从而使该人存在道德义务或自然义务。该种对价通常是不可强制执行的[unenforceable ]。亦作“meritorious consideration” 或“moral consideration”。②有效对价 指足以支持当事 人之间交易的对价即“valuable consideration”

valuable consideration充分对价;有效对价。指根据法律规定属于有效之对价，它既可以是对一方当事人给予某种可用金钱衡量的权利、利益，也可以是另一方承受某种可用金钱衡量的损害、不利益、责任或放弃行使权利。它有时与道德对价[good consideration]相区别。

英英释义

good consideration

1: a consideration based on a family relationship or natural love and affection

2: valuable consideration in this entry

NOTE: As defined in sense 1, good consideration is the opposite of valuable consideration, though it is sometimes used to mean valuable consideration. Good consideration of the kind denoted by sense 1 cannot create an enforceable contract.

https://www.merriam-webster.com/dictionary/consideration#legalDictionary

valuable consideration

an equivalent or compensation having value that is given for something acquired or promised (such as money or marriage) and that may consist either in a benefit accruing to one party or a loss falling upon the other

https://www.merriam-webster.com/dictionary/valuable%20consideration

consideration

something (as an act or forbearance or the promise thereof) done or given by one party for the act or promise of another

https://www.merriam-webster.com/dictionary/consideration#legalDictionary

对价(consideration)原本是英美合同法中的重要概念，其内涵是一方为换取另一方做某事的承诺而向另一方支付的金钱代价或得到该种承诺的代价。 指当事人一方在获得某种利益时，必须给付对方相应的代价。

https://baike.baidu.com/item/%E5%AF%B9%E4%BB%B7