breathing device vs device

breathing device and device both are nouns.

Word	Noun	Adjective	Verb	Adverb
breathing device	Yes	No	No	No
device	Yes	No	No	No

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

breathing device: a device that facilitates breathing in cases of respiratory failure
device: an instrumentality invented for a particular purpose

breathing device (noun)	device (noun)
a device that facilitates breathing in cases of respiratory failure	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