supreme authority vs expert

supreme authority and expert both are nouns.

Word	Noun	Adjective	Verb	Adverb
supreme authority	Yes	No	No	No
expert	Yes	Yes	No	No

As nouns, expert is a hypernym of supreme authority; that is, expert is a word with a broader meaning than supreme authority:

supreme authority (noun)	expert (noun)
someone with the power to settle matters at will	a person with special knowledge or ability who performs skillfully

supreme authority (adjective)	expert (adjective)
	having or showing knowledge and skill and aptitude
	of or relating to or requiring special knowledge to be understood