evaluator vs arbitrator

evaluator and arbitrator both are nouns.

Word	Noun	Adjective	Verb	Adverb
evaluator	Yes	No	No	No
arbitrator	Yes	No	No	No

As nouns, arbitrator is a hyponym of evaluator; that is, arbitrator is a word with a more specific, narrower meaning than evaluator:

Other hyponyms of evaluator include appraiser, valuator, arbiter, umpire, critic.

evaluator (noun)	arbitrator (noun)
an authority who is able to estimate worth or quality	someone chosen to judge and decide a disputed issue