political sphere vs domain

political sphere and domain both are nouns.

Word	Noun	Adjective	Verb	Adverb
political sphere	Yes	No	No	No
domain	Yes	No	No	No

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

Other hypernyms of political sphere include area, arena, field, orbit, sphere.

political sphere (noun)	domain (noun)
a sphere of intense political activity	the content of a particular field of knowledge
	people in general; especially a distinctive group of people with some shared interest
	(mathematics) the set of values of the independent variable for which a function is defined
	territory over which rule or control is exercised
	a particular environment or walk of life