hairtail vs percoid

hairtail and percoid both are nouns.

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

As nouns, percoid is a hypernym of hairtail; that is, percoid 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
percoid: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of hairtail include percoid fish, percoidean.

hairtail (noun)	percoid (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