domain vs region

domain and region both are nouns.

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

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

domain: the content of a particular field of knowledge
region: a knowledge domain that you are interested in or are communicating about

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

domain (noun)	region (noun)
the content of a particular field of knowledge	a part of an animal that has a special function or is supplied by a given artery or nerve
people in general; especially a distinctive group of people with some shared interest	a knowledge domain that you are interested in or are communicating about
(mathematics) the set of values of the independent variable for which a function is defined	the extended spatial location of something
territory over which rule or control is exercised	a large indefinite location on the surface of the Earth
a particular environment or walk of life	the approximate amount of something (usually used prepositionally as in `in the region of')