quasi 对应的中文为“仿佛；类似；准；半”，此词用作法律术语，表明一物虽然在某些特征方面类似另一物，但它们之间有内在和实质的不同。该词常置于英文词的前面，表示加此缀的概念与原概念在形式上极为类似。

Quasi Contract 在《元照英美法词典》中给出的中文是：准契约；准合同

给出的解释是：即拉丁文「quasi ex contractus」。指在无协议的情况下，基于公平和正义所产生的法律义务。通常是为了防止发生不当得利而由法律设定的合同义务。有时指法律上默许的契约，成为法律上的拟制。法律拟制即在无真正契约存在的情况下，采用契约诉讼的手段，以取得公平和法律义务的履行。

Investopedia中给出的英文释义好像比较通俗易懂一些：

A quasi contract is a retroactive arrangement between two parties who have no previous obligations to one another. It is created by a judge to correct a circumstance in which one party acquires something at the expense of the other.

The contract aims to prevent one party from unfairly benefiting from the situation at the other party's expense. These arrangements may be imposed when goods or services are accepted, though not requested, by a party. The acceptance then creates an expectation of payment.

参考译文：准合同是双方之间的一种追溯性安排，双方之前没有相互的义务。它是法官为了纠正一方以牺牲另一方的利益而获得某种东西的情况而创立的。

该合同旨在防止一方在损害另一方利益的情况下不公平地从中获益。该等安排可于一方接受货品或服务(尽管并非要求)时实施。承兑则产生付款之预期。

可以来看一个例子，感受一下quasi contract的使用场景！

A classic quasi contract circumstance may be created by the delivery of a pizza to the wrong address—that is, not to the person who paid for it. If the individual at the incorrect address fails to fess to the error and instead keeps the pizza, they could be seen as having accepted the food, and thus be obliged to pay for it. A court could then rule to issue a quasi contract that requires the pizza recipient to pay back the cost of the food to the party who purchased it or to the pizzeria if it subsequently delivered a second pie to the purchaser. The restitution mandated under the quasi contract aims for a fair resolution of the situation.

一个典型的准合同情况可能是由于将比萨饼送到了错误的地址--也就是说，没有送到付钱的人那里。如果送错地址的人没有承认错误，而是保留了比萨饼，他们就会被视为接受了食物，从而有义务为其付费。然后，法院可以裁定签发一份准合同，要求接受比萨饼的人向购买比萨饼的一方偿还食物的费用，或者如果比萨饼店后来向购买者交付了第二个比萨饼，则向其偿还。准合同规定的赔偿旨在公平解决这种情况。

双语例句：

The Court has jurisdiction to hear and determine any action founded on contract, quasi-contract or tort where the amount of the plaintiff's claim does not exceed $600,000. 

在建议的第32条中 ─ “(1)凡在任何基于合约、准合约或侵权行为而提出的诉讼中，原告人申索的款额不超逾$600,000，区域法院具有聆讯和裁定该诉讼的司法管辖权。

Troublesome cases that may or may not be examples of quasi-contract include, for example, (a) where one surety claims a contribution from another surety with whom he has no contract (b) where someone seeks to be paid for services rendered under a contract that turns out to be void (c) where a judgment creditor brings an action to recover a judgment debt.

麻烦的个案极多，一些或可作为准合同的例子，而另一些则不可，这些个案包括：( a )一名保证人要求另一名保证人分担赔偿责任，但前者并没有跟后者缔结合同；( b )某人索取其按合同提供服务的酬金，但后来该合同证实无效；( c )胜诉债权人采取法律行动，追讨经法庭裁定的债务。