cargo liner vs ocean liner

cargo liner and ocean liner both are nouns.

Word	Noun	Adjective	Verb	Adverb
cargo liner	Yes	No	No	No
ocean liner	Yes	No	No	No

As nouns, ocean liner is a hypernym of cargo liner; that is, ocean liner is a word with a broader meaning than cargo liner:

cargo liner: a liner that carries cargo
ocean liner: a large commercial ship (especially one that carries passengers on a regular schedule)

Other hypernyms of cargo liner include liner.

cargo liner (noun)	ocean liner (noun)
a liner that carries cargo	a large commercial ship (especially one that carries passengers on a regular schedule)