Common law
The common lawso named because it was "common" to all the king's courts across Englandoriginated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066. The British Empire spread the English legal system to its historical colonies, many of which retain the common law system today. These "common law systems" are legal systems that give great precedential weight to common law, and to the style of reasoning inherited from the English legal system.
Common law
The term "common law" is often used as a contrast to Roman-derived "civil law", and the fundamental processes and forms of reasoning in the two are quite different. Nonetheless, there has been considerable cross-fertilization of ideas, while the two traditions and sets of foundational principles remain distinct.