demesne vs realty

demesne and realty both are nouns.

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

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

demesne: extensive landed property (especially in the country) retained by the owner for his own use
realty: property consisting of houses and land

Other hypernyms of demesne include immovable, real estate, real property.

demesne (noun)	realty (noun)
territory over which rule or control is exercised	property consisting of houses and land
extensive landed property (especially in the country) retained by the owner for his own use