supreme authority vs arbiter

supreme authority and arbiter both are nouns.

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

As nouns, supreme authority and arbiter are synonyms defined as:

supreme authority and arbiter: someone with the power to settle matters at will

supreme authority (noun)	arbiter (noun)
someone with the power to settle matters at will	someone chosen to judge and decide a disputed issue
	someone with the power to settle matters at will