coop vs squirrel cage

coop and squirrel cage both are nouns.

Word	Noun	Adjective	Verb	Adverb
coop	Yes	No	No	No
squirrel cage	Yes	No	No	No

As nouns, squirrel cage is a hyponym of coop; that is, squirrel cage is a word with a more specific, narrower meaning than coop:

coop: an enclosure made or wire or metal bars in which birds or animals can be kept
squirrel cage: cage with a cylindrical framework that rotates as a small animal runs inside it

Other hyponyms of coop include birdcage, hutch.

coop (noun)	squirrel cage (noun)
an enclosure made or wire or metal bars in which birds or animals can be kept	cage with a cylindrical framework that rotates as a small animal runs inside it
a farm building for housing poultry