promissum

Promissum is a noun of Latin origin meaning "a promise" or "the thing promised." It comes from promiss- from promittere, with promissus as the past participle and promissum as the neuter noun form. In Latin literature, promissum signified a formal undertaking by which one party bound itself to perform a future act, and it appears in contractual and legal contexts throughout late antiquity and the medieval period.

In Roman law and in medieval legal documents, promissum was used to denote a binding promise, often expressed in writing or sealings of charters. It could function as the basis of an obligation or as part of a contract, sometimes alongside other conditions, guarantees, or penalties.

In modern usage, the Latin term is largely encountered in linguistic, historical, or legal-historical work. The practical concept is now usually described in English as a promissory note or simply a promise to perform—an obligation by which one party commits to render a given act or payment to another. The term promissum thus serves as a historical reference point for how promises were conceptualized and documented in classical and medieval law and in discussions of Latin legal vocabulary.