seigneury vs demesne

seigneury and demesne both are nouns.

Word	Noun	Adjective	Verb	Adverb
seigneury	Yes	No	No	No
demesne	Yes	No	No	No

As nouns, demesne is a hypernym of seigneury; that is, demesne is a word with a broader meaning than seigneury:

seigneury: the estate of a seigneur
demesne: extensive landed property (especially in the country) retained by the owner for his own use

Other hypernyms of seigneury include acres, estate, land, landed estate.

seigneury (noun)	demesne (noun)
the position and authority of a feudal lord	territory over which rule or control is exercised
the estate of a seigneur	extensive landed property (especially in the country) retained by the owner for his own use