serf vs villein

serf and villein both are nouns.

Word	Noun	Adjective	Verb	Adverb
serf	Yes	No	No	No
villein	Yes	No	No	No

As nouns, serf and villein are synonyms defined as:

serf and villein: (Middle Ages) a person who is bound to the land and owned by the feudal lord

Other synonyms of serf include helot.

serf (noun)	villein (noun)
(Middle Ages) a person who is bound to the land and owned by the feudal lord	(Middle Ages) a person who is bound to the land and owned by the feudal lord