dolphin vs percoid

dolphin and percoid both are nouns.

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

As nouns, percoid is a hypernym of dolphin; that is, percoid is a word with a broader meaning than dolphin:

dolphin: large slender food and game fish widely distributed in warm seas (especially around Hawaii)
percoid: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of dolphin include percoid fish, percoidean.

dolphin (noun)	percoid (noun)
any of various small toothed whales with a beaklike snout; larger than porpoises	any of numerous spiny-finned fishes of the order Perciformes
large slender food and game fish widely distributed in warm seas (especially around Hawaii)