bluefin tuna vs tuna

bluefin tuna and tuna both are nouns.

Word	Noun	Adjective	Verb	Adverb
bluefin tuna	Yes	No	No	No
tuna	Yes	No	No	No

As nouns, tuna is a hypernym of bluefin tuna; that is, tuna is a word with a broader meaning than bluefin tuna:

bluefin tuna: largest tuna; to 1500 pounds; of mostly temperate seas: feed in polar regions but breed in tropics
tuna: any very large marine food and game fish of the genus Thunnus; related to mackerel; chiefly of warm waters

Other hypernyms of bluefin tuna include tunny.

As nouns, tuna is a hypernym of bluefin tuna; that is, tuna is a word with a broader meaning than bluefin tuna:

bluefin tuna: flesh of very large tuna
tuna: important warm-water fatty fish of the genus Thunnus of the family Scombridae; usually served as steaks

Other hypernyms of bluefin tuna include tuna fish, tunny.

bluefin tuna (noun)	tuna (noun)
largest tuna; to 1500 pounds; of mostly temperate seas: feed in polar regions but breed in tropics	any very large marine food and game fish of the genus Thunnus; related to mackerel; chiefly of warm waters
flesh of very large tuna	New Zealand eel
	important warm-water fatty fish of the genus Thunnus of the family Scombridae; usually served as steaks
	tropical American prickly pear of Jamaica