There is no commonly accepted modern definition of feudalism, at least among scholars. The adjective feudal was coined in the 17th century, and the noun feudalism, often used in a political and propaganda context, was not coined until the 19th century, from the French féodalité (feudality), itself an 18th-century creation.
In a classic definition by François-Louis Ganshof (1944), feudalism describes a set of reciprocal legal and military obligations among the warrior nobility, revolving around the three key concepts of lords, vassals and fiefs, though Ganshof himself noted that his treatment related only to the "narrow, technical, legal sense of the word".
A broader definition, as described in Marc Bloch's Feudal Society (1939), includes not only the obligations of the warrior nobility but those of all three estates of the realm: the nobility, the clergy, and those living by their labour, most directly the peasantry bound by manorialism; this order is often referred to as "feudal society", echoing Bloch's usage.
Outside of a European context, the concept of feudalism is often used by analogy, most often in discussions of feudal Japan under the shōguns, and sometimes Zagwe dynasty in medieval Ethiopia, which had some feudal characteristics (sometimes called "semifeudal"). Some have taken the feudalism analogy further, seeing feudalism (or traces of it) in places as diverse as Spring and Autumn period in China, ancient Egypt, the Parthian empire, the Indian subcontinent and the Antebellum and Jim Crow American South. Wu Ta-k'un argued that China's fengjian, being kinship-based and tied to land controlled by the king, were entirely distinct from feudalism. This despite the fact that in translation fengjian is frequently paired in both directions with feudal.
The term feudalism has also been applied—often inappropriately or pejoratively—to non-Western societies where institutions and attitudes similar to those of medieval Europe are perceived to prevail. Some historians and political theorists believe that the term feudalism has been deprived of specific meaning by the many ways it has been used, leading them to reject it as a useful concept for understanding society.