owner vs part-owner

owner and part-owner both are nouns.

Word	Noun	Adjective	Verb	Adverb
owner	Yes	No	No	No
part-owner	Yes	No	No	No

As nouns, part-owner is a hyponym of owner; that is, part-owner is a word with a more specific, narrower meaning than owner:

Other hyponyms of owner include holder, homeowner, householder, saver, shipowner.

owner (noun)	part-owner (noun)
(law) someone who owns (is legal possessor of) a business	a person who owns something in common with others
a person who owns something