water cooler vs device

water cooler and device both are nouns.

Word	Noun	Adjective	Verb	Adverb
water cooler	Yes	No	No	No
device	Yes	No	No	No

As nouns, device is a hypernym of water cooler; that is, device is a word with a broader meaning than water cooler:

water cooler (noun)	device (noun)
a device for cooling and dispensing drinking water	any clever maneuver
	an instrumentality invented for a particular purpose
	an emblematic design (especially in heraldry)
	any ornamental pattern or design (as in embroidery)
	something in an artistic work designed to achieve a particular effect