serf vs cottier

serf and cottier both are nouns.

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

As nouns, cottier is a hyponym of serf; that is, cottier is a word with a more specific, narrower meaning than serf:

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

Other hyponyms of serf include cotter.

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