fin whale vs rorqual

fin whale and rorqual both are nouns.

Word	Noun	Adjective	Verb	Adverb
fin whale	Yes	No	No	No
rorqual	Yes	No	No	No

As nouns, rorqual is a hypernym of fin whale; that is, rorqual is a word with a broader meaning than fin whale:

fin whale: large flat-headed whalebone whale having deep furrows along the throat; of Atlantic and Pacific
rorqual: any of several baleen whales of the family Balaenopteridae having longitudinal grooves on the throat and a small pointed dorsal fin

Other hypernyms of fin whale include razorback.

fin whale (noun)	rorqual (noun)
large flat-headed whalebone whale having deep furrows along the throat; of Atlantic and Pacific	any of several baleen whales of the family Balaenopteridae having longitudinal grooves on the throat and a small pointed dorsal fin