auto accessory vs appurtenance

auto accessory and appurtenance both are nouns.

Word	Noun	Adjective	Verb	Adverb
auto accessory	Yes	No	No	No
appurtenance	Yes	No	No	No

As nouns, appurtenance is a hypernym of auto accessory; that is, appurtenance is a word with a broader meaning than auto accessory:

Other hypernyms of auto accessory include accessory, add-on, supplement.

auto accessory (noun)	appurtenance (noun)
an accessory for an automobile	a supplementary component that improves capability
	equipment consisting of miscellaneous articles needed for a particular operation or sport etc.