Unjust Enrichment，法律术语，不当得利。

Unjust Enrichment：profit unjustly obtain by a wrongdoer. To obtain reimbursement, the plaintiff must show an actual benefit to the defendant, a corresponding loss to the plaintiff and the absence of a legal reason for the defendant's enrichment.

不当得利，指没有合法根据，或事后丧失了合法根据而被确认为是因致他人遭受损失而获得的利益。如售货时多收货款，拾得遗失物据为己有等。取得利益的人称受益人，遭受损害的人称受害人。不当得利的取得，不是由于受益人针对受害人而为的违法行为，而是由于受害人或第三人的疏忽、误解或过错所造成的。受益人与受害人之间因此形成债的关系，受益人为债务人（debtor），受害人为债权人（creditor）。

参考双语例句：

Nicaragua further indicates that it “reserves the right to claim compensation for elements of unjust enrichment consequent upon Colombian possession of the Islands of San Andrés and Providencia as well as the keys and maritime spaces up to the 82 meridian, in the absence of lawful title”.

尼加拉瓜还表示，它“保留就哥伦比亚在没有合法所有权的情况下占有圣安德烈斯岛和普罗维登西亚岛以及直至 82 度经线以内的礁群和海洋空间而获取的各项不当利益提出索赔的权利”，并且“保留就尼加拉瓜国籍渔船或尼加拉瓜发照的船只受到的干预提出索赔的权利”。

Until such withdrawal, the licensee has to pay for the use of the licensed intellectual property on the basis of the principle of unjust enrichment an amount equal to the royalties owed under the licence agreement that was rejected.

直至撤销之前，被许可人必须根据不当得利原则，为使用被许可使用的知识产权付费，数额相当于按照被取消的许可协议应当支付的许可使用费。

The Government explained that there had been no acts of unjust enrichment with the award of the contract and that any breaches of the procurement rules were inadvertent and arose from a need to meet a 20 December 2007 deadline imposed by the new Government for the supply of electricity to Freetown.

政府解释说，在该合同的授予过程中未出现中饱私囊行为，即便存在任何违反采购规则的做法也都是无意的，而且也是因为必须遵守新政府所规定的于2007年12月20日实现向弗里敦供电的最后期限。

An Shin then filed a lawsuit to the court and confirmed that TCIFI did not own the creditor’s right and required TCIFI to pay back the unjust enrichment of $3,595 thousand.

安欣公司因而向法院提貣诉讼确认大众租赁之债权不存在，并请求返还该不当得利3,595千元。