heir vs successor

heir and successor both are nouns.

Word	Noun	Adjective	Verb	Adverb
heir	Yes	No	No	No
successor	Yes	No	No	No

As nouns, heir and successor are synonyms defined as:

heir (noun)	successor (noun)
a person who is entitled by law or by the terms of a will to inherit the estate of another	a thing or person that immediately replaces something or someone
a person who inherits some title or office	a person who inherits some title or office
	a person who follows next in order