brown trout vs trout

brown trout and trout both are nouns.

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

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

brown trout: speckled trout of European rivers; introduced in North America
trout: any of various game and food fishes of cool fresh waters mostly smaller than typical salmons

brown trout (noun)	trout (noun)
speckled trout of European rivers; introduced in North America	any of various game and food fishes of cool fresh waters mostly smaller than typical salmons
	flesh of any of several primarily freshwater game and food fishes