yellowfin tuna vs tuna

yellowfin tuna and tuna both are nouns.

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

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

yellowfin tuna: may reach 400 pounds; worldwide 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 yellowfin tuna include tunny.

yellowfin tuna (noun)	tuna (noun)
may reach 400 pounds; worldwide in tropics	any very large marine food and game fish of the genus Thunnus; related to mackerel; chiefly of warm waters
	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