gizmo vs device

gizmo and device both are nouns.

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

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

gizmo (noun)	device (noun)
a device or control that is very useful for a particular job	any clever maneuver
something unspecified whose name is either forgotten or not known	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