tripletail vs percoidean

tripletail and percoidean both are nouns.

Word	Noun	Adjective	Verb	Adverb
tripletail	Yes	No	No	No
percoidean	Yes	No	No	No

As nouns, percoidean is a hypernym of tripletail; that is, percoidean is a word with a broader meaning than tripletail:

tripletail: large food fish of warm waters worldwide having long anal and dorsal fins that with a caudal fin suggest a three-lobed tail
percoidean: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of tripletail include percoid, percoid fish.

tripletail (noun)	percoidean (noun)
large food fish of warm waters worldwide having long anal and dorsal fins that with a caudal fin suggest a three-lobed tail	any of numerous spiny-finned fishes of the order Perciformes