major power vs great power

major power and great power both are nouns.

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

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

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

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

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