brook trout vs trout

brook trout and trout both are nouns.

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

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

brook trout: North American freshwater trout; introduced in Europe
trout: any of various game and food fishes of cool fresh waters mostly smaller than typical salmons

brook trout (noun)	trout (noun)
North American freshwater trout; introduced in Europe	any of various game and food fishes of cool fresh waters mostly smaller than typical salmons
a delicious freshwater food fish	flesh of any of several primarily freshwater game and food fishes