arborist vs specialist

arborist and specialist both are nouns.

Word	Noun	Adjective	Verb	Adverb
arborist	Yes	No	No	No
specialist	Yes	No	No	No

As nouns, specialist is a hypernym of arborist; that is, specialist is a word with a broader meaning than arborist:

arborist: a specialist in treating damaged trees
specialist: an expert who is devoted to one occupation or branch of learning

Other hypernyms of arborist include specialiser, specializer.

arborist (noun)	specialist (noun)
a specialist in treating damaged trees	an expert who is devoted to one occupation or branch of learning
	practices one branch of medicine