rider vs hitchhiker

rider and hitchhiker both are nouns.

Word	Noun	Adjective	Verb	Adverb
rider	Yes	No	No	No
hitchhiker	Yes	No	No	No

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

rider: a traveler riding in a vehicle (a boat or bus or car or plane or train etc) who is not operating it
hitchhiker: a person who travels by getting free rides from passing vehicles

Other hyponyms of rider include commuter, fare, stowaway, straphanger.

rider (noun)	hitchhiker (noun)
a clause that is appended to a legislative bill	a person who travels by getting free rides from passing vehicles
a traveler who actively rides an animal (as a horse or camel)
a traveler riding in a vehicle (a boat or bus or car or plane or train etc) who is not operating it
a traveler who actively rides a vehicle (as a bicycle or motorcycle)