fiefdom vs domain

fiefdom and domain both are nouns.

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

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

Other hypernyms of fiefdom include demesne, land.

fiefdom (noun)	domain (noun)
an organization that is controlled by a dominant person or group	the content of a particular field of knowledge
the domain controlled by a feudal lord	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