fish vs trout

fish and trout both are nouns.

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

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

fish (noun)	trout (noun)
any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills	any of various game and food fishes of cool fresh waters mostly smaller than typical salmons
the flesh of fish used as food	flesh of any of several primarily freshwater game and food fishes

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