oiler vs cargo ship

oiler and cargo ship both are nouns.

Word	Noun	Adjective	Verb	Adverb
oiler	Yes	No	No	No
cargo ship	Yes	No	No	No

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

Other hypernyms of oiler include cargo vessel.

oiler (noun)	cargo ship (noun)
a cargo ship designed to carry crude oil in bulk	a ship designed to carry cargo
a well that yields or has yielded oil
a worker who oils engines or machinery