A more thorough explanation:

Definition: Usus Feudorum is a Latin term that refers to the Books of Feuds, a compilation of Lombardic feudal law published in Milan around 1152 during the reign of Henry III. It was the main source of tenure law among the nations in Europe and widely used in medieval law schools and courts in Italy, France, and Germany. The Feudorum Libri had little effect on English law but influenced English lawyers to study their own tenure system more critically.

Example: The Usus Feudorum or Feudorum Libri was a significant legal text in medieval Europe. It was used to determine the rights and obligations of lords and vassals in feudal relationships. For example, it outlined the rules for inheritance of fiefs, the duties of vassals to their lords, and the rights of lords to demand military service from their vassals.

Explanation: The example illustrates how the Usus Feudorum was used to establish the legal framework for feudal relationships in medieval Europe. It provided guidance on the rights and obligations of lords and vassals, which were essential to maintaining the feudal system. The Feudorum Libri was a crucial source of law that helped to shape the legal systems of many European countries.