trout vs fish

trout and fish both are nouns.

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

As nouns, fish is a hypernym of trout; that is, fish is a word with a broader meaning than trout:

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

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