passenger vs stowaway

passenger and stowaway both are nouns.

Word	Noun	Adjective	Verb	Adverb
passenger	Yes	No	No	No
stowaway	Yes	No	No	No

As nouns, stowaway is a hyponym of passenger; that is, stowaway is a word with a more specific, narrower meaning than passenger:

passenger: a traveler riding in a vehicle (a boat or bus or car or plane or train etc) who is not operating it
stowaway: a person who hides aboard a ship or plane in the hope of getting free passage

Other hyponyms of passenger include commuter, fare, hitchhiker, straphanger.

passenger (noun)	stowaway (noun)
a traveler riding in a vehicle (a boat or bus or car or plane or train etc) who is not operating it	a person who hides aboard a ship or plane in the hope of getting free passage