demesne vs region

demesne and region both are nouns.

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

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

demesne (noun)	region (noun)
territory over which rule or control is exercised	a part of an animal that has a special function or is supplied by a given artery or nerve
extensive landed property (especially in the country) retained by the owner for his own use	a knowledge domain that you are interested in or are communicating about
	the extended spatial location of something
	a large indefinite location on the surface of the Earth
	the approximate amount of something (usually used prepositionally as in `in the region of')