A quasi-contract (or implied-in-law contract or constructive contract) is a fictional contract recognised by a court. The notion of a quasi-contract can be traced to Roman law and is still a concept used in some modern legal systems. Quasi contract laws have been deduced from the Latin statement "Nemo debet locupletari ex aliena iactura", which proclaims that no one should grow rich out of another person's loss. It was one of the central doctrines of Roman law.