publishing empire vs empire

publishing empire and empire both are nouns.

Word	Noun	Adjective	Verb	Adverb
publishing empire	Yes	No	No	No
empire	Yes	No	No	No

As nouns, empire is a hypernym of publishing empire; that is, empire is a word with a broader meaning than publishing empire:

publishing empire: a conglomerate of publishing companies
empire: a group of diverse companies under common ownership and run as a single organization

Other hypernyms of publishing empire include conglomerate.

publishing empire (noun)	empire (noun)
a conglomerate of publishing companies	a monarchy with an emperor as head of state
	a group of countries under a single authority
	a group of diverse companies under common ownership and run as a single organization
	the domain ruled by an emperor or empress; the region over which imperial dominion is exercised