fish vs stockfish

fish and stockfish both are nouns.

Word	Noun	Adjective	Verb	Adverb
fish	Yes	No	Yes	No
stockfish	Yes	No	No	No

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

fish (noun)	stockfish (noun)
any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills	fish cured by being split and air-dried without salt
the flesh of fish used as food

fish (verb)	stockfish (verb)
catch or try to catch fish or shellfish
seek indirectly