arbiter vs supreme authority

arbiter and supreme authority both are nouns.

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

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

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

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