Laesio

Laesio is a Latin term meaning injury or harm, commonly used in legal history to refer to damage arising in a transaction or contract. The root verb laedere, “to injure,” underpins the term’s usage in classical and civil-law contexts, where it denotes unfair or excessive disadvantage arising from an agreement.

A well-known application is laesio enormis, a doctrine found in Roman law and influencing medieval and continental civil-law systems. It describes a situation in which one party’s consideration in a contract is grossly disproportionate to the actual value of the thing exchanged, potentially allowing relief such as rescission or adjustment of the price. The remedy depended on the absence of fraud and other facts, and the precise rules varied across jurisdictions and periods.

In later legal development, laesio and laesio enormis contributed to broader notions of fairness in bargaining. Modern civil-code jurisdictions often address gross unfairness through general doctrines of good faith, undue influence, mistake, or specific consumer-protection rules, rather than by applying the historic term laesio as a standalone, operative doctrine.

Beyond contract law, laesio continues to appear in legal-historical and linguistic discussions as a representation of injury or harm within bargaining and other relationships. The term remains a reference point for understanding how ancient and medieval systems conceptualized and tempered exploitation in agreements.

Etymology: from Latin laedere, to injure. The noun laesio appears in legal texts to denote harm arising in contracts or exchanges.