Unjust enrichment is a legal term in English law and in several other jurisdictions, denoting a particular type of causative event in which one party is unjustly enriched at the expense of another, and an obligation to make restitution arises, regardless of liability for wrongdoing.
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A legal procedure whereby you can seek reimbursement from another who benefitted from your action or property without legal justification. - (read more on Unjust enrichment)