millionaire vs rich person

millionaire and rich person both are nouns.

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

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

millionaire: a person whose material wealth is valued at more than a million dollars
rich person: a person who possesses great material wealth

Other hypernyms of millionaire include adult male, man, have, wealthy person.

millionaire (noun)	rich person (noun)
a person whose material wealth is valued at more than a million dollars	a person who possesses great material wealth