billionaire vs rich person

billionaire and rich person both are nouns.

Word	Noun	Adjective	Verb	Adverb
billionaire	Yes	No	No	No
rich person	Yes	No	No	No

As nouns, rich person is a hypernym of billionaire; that is, rich person is a word with a broader meaning than billionaire:

billionaire: a very rich person whose material wealth is valued at more than a billion dollars
rich person: a person who possesses great material wealth

Other hypernyms of billionaire include have, wealthy person.

billionaire (noun)	rich person (noun)
a very rich person whose material wealth is valued at more than a billion dollars	a person who possesses great material wealth