first lady vs succeeder

first lady and succeeder both are nouns.

Word	Noun	Adjective	Verb	Adverb
first lady	Yes	No	No	No
succeeder	Yes	No	No	No

As nouns, succeeder is a hypernym of first lady; that is, succeeder is a word with a broader meaning than first lady:

Other hypernyms of first lady include achiever, success, winner.

first lady (noun)	succeeder (noun)
the wife of a chief executive	a person with a record of successes
the leading woman in an art or profession