feudal system vs feudalism

feudal system and feudalism both are nouns.

Word	Noun	Adjective	Verb	Adverb
feudal system	Yes	No	No	No
feudalism	Yes	No	No	No

As nouns, feudal system and feudalism are synonyms defined as:

feudal system and feudalism: the social system that developed in Europe in the 8th century; vassals were protected by lords who they had to serve in war

feudal system (noun)	feudalism (noun)
the social system that developed in Europe in the 8th century; vassals were protected by lords who they had to serve in war	the social system that developed in Europe in the 8th century; vassals were protected by lords who they had to serve in war