bony fish vs lungfish

bony fish and lungfish both are nouns.

Word	Noun	Adjective	Verb	Adverb
bony fish	Yes	No	No	No
lungfish	Yes	No	No	No

As nouns, lungfish is a hyponym of bony fish; that is, lungfish is a word with a more specific, narrower meaning than bony fish:

bony fish: any fish of the class Osteichthyes
lungfish: air-breathing fish having an elongated body and fleshy paired fins; certain species construct mucus-lined mud coverings in which to survive drought

Other hyponyms of bony fish include crossopterygian, lobe-finned fish, lobefin, teleost, teleost fish, teleostan.

bony fish (noun)	lungfish (noun)
any fish of the class Osteichthyes	air-breathing fish having an elongated body and fleshy paired fins; certain species construct mucus-lined mud coverings in which to survive drought