arbiter vs expert

arbiter and expert both are nouns.

Word	Noun	Adjective	Verb	Adverb
arbiter	Yes	No	No	No
expert	Yes	Yes	No	No

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

arbiter (noun)	expert (noun)
someone chosen to judge and decide a disputed issue	a person with special knowledge or ability who performs skillfully
someone with the power to settle matters at will

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