ferryboat vs car-ferry

ferryboat and car-ferry both are nouns.

Word	Noun	Adjective	Verb	Adverb
ferryboat	Yes	No	No	No
car-ferry	Yes	No	No	No

As nouns, car-ferry is a hyponym of ferryboat; that is, car-ferry is a word with a more specific, narrower meaning than ferryboat:

ferryboat: a boat that transports people or vehicles across a body of water and operates on a regular schedule
car-ferry: a ferry that transports motor vehicles

ferryboat (noun)	car-ferry (noun)
a boat that transports people or vehicles across a body of water and operates on a regular schedule	a ferry that transports motor vehicles