passenger vs traveller

passenger and traveller both are nouns.

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

As nouns, traveller is a hypernym of passenger; that is, traveller is a word with a broader 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
traveller: a person who changes location

Other hypernyms of passenger include traveler.

passenger (noun)	traveller (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 changes location