great power vs world power

great power and world power both are nouns.

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

As nouns, great power and world power are synonyms defined as:

great power and world power: a state powerful enough to influence events throughout the world

Other synonyms of great power include major power, power, superpower.

great power (noun)	world power (noun)
a state powerful enough to influence events throughout the world	a state powerful enough to influence events throughout the world