Decretum

Decretum is a Latin term meaning "decree" or "order," used in civil and ecclesiastical contexts to denote a formal decision issued by a competent authority. In medieval canon law, the term is most closely associated with Gratian's Decretum, usually called the Decretum Gratianum, a large compilation of canonical canons assembled around 1140–1150 by the scholar Gratian (Gratianus).

Gratian's work collects thousands of canons from earlier Church authorities, councils, and papal decretals, and arranges them topically to show harmonies and contradictions. The Decretum thereby functioned as a foundational teaching text for students and practitioners of canon law for several centuries, shaping legal method and argument.

The Decretum was expanded and glossed by later medieval jurists—the glossators and their scholastic successors—whose commentaries helped transform it into a living manual. It remained authoritative even after the appearance of official compilations such as the Decretals of Gregory IX (the Liber Extra) and the later Corpus Juris Canonici, but Gratian's Decretum continued to be a central reference.

Beyond Gratian, "decretum" is a generic term for decrees issued by sovereigns or church authorities; many documents in Latin use the word as a formal designation. In modern usage, the term appears mainly in historical or scholarly contexts to reference this and other similar collections of decrees.