hairtail vs percoidean

hairtail and percoidean both are nouns.

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

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

hairtail: long-bodied marine fishes having a long whiplike scaleless body and sharp teeth; closely related to snake mackerel
percoidean: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of hairtail include percoid, percoid fish.

hairtail (noun)	percoidean (noun)
long-bodied marine fishes having a long whiplike scaleless body and sharp teeth; closely related to snake mackerel	any of numerous spiny-finned fishes of the order Perciformes