supreme vs sovereign

supreme is not a noun while sovereign is a noun.

Word	Noun	Adjective	Verb	Adverb
supreme	No	Yes	No	No
sovereign	Yes	Yes	No	No

As adjectives, supreme and sovereign are synonyms defined as:

supreme (noun)	sovereign (noun)
	a nation's ruler or head of state usually by hereditary right

supreme (adjective)	sovereign (adjective)
greatest in status or authority or power	greatest in status or authority or power
greatest or maximal in degree; extreme	(of political bodies) not controlled by outside forces
highest in excellence or achievement
final or last in your life or progress