differential gear vs bevel gear

differential gear and bevel gear both are nouns.

Word	Noun	Adjective	Verb	Adverb
differential gear	Yes	No	No	No
bevel gear	Yes	No	No	No

As nouns, bevel gear is a hypernym of differential gear; that is, bevel gear is a word with a broader meaning than differential gear:

differential gear: a bevel gear that permits rotation of two shafts at different speeds; used on the rear axle of automobiles to allow wheels to rotate at different speeds on curves
bevel gear: gears that mesh at an angle

Other hypernyms of differential gear include pinion and crown wheel, pinion and ring gear.

differential gear (noun)	bevel gear (noun)
a bevel gear that permits rotation of two shafts at different speeds; used on the rear axle of automobiles to allow wheels to rotate at different speeds on curves	gears that mesh at an angle