great power vs hegemon

great power and hegemon both are nouns.

Word	Noun	Adjective	Verb	Adverb
great power	Yes	No	No	No
hegemon	Yes	No	No	No

As nouns, hegemon is a hyponym of great power; that is, hegemon is a word with a more specific, narrower meaning than great power:

great power: a state powerful enough to influence events throughout the world
hegemon: a leading or paramount power

great power (noun)	hegemon (noun)
a state powerful enough to influence events throughout the world	a leading or paramount power