countryseat vs demesne

countryseat and demesne both are nouns.

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

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

countryseat: an estate in the country
demesne: extensive landed property (especially in the country) retained by the owner for his own use

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

countryseat (noun)	demesne (noun)
an estate in the country	territory over which rule or control is exercised
	extensive landed property (especially in the country) retained by the owner for his own use