auto vs car

auto and car both are nouns.

Word	Noun	Adjective	Verb	Adverb
auto	Yes	No	No	No
car	Yes	No	No	No

As nouns, auto and car are synonyms defined as:

auto and car: a motor vehicle with four wheels; usually propelled by an internal combustion engine

Other synonyms of auto include automobile, machine, motorcar.

auto (noun)	car (noun)
a motor vehicle with four wheels; usually propelled by an internal combustion engine	a motor vehicle with four wheels; usually propelled by an internal combustion engine
	a wheeled vehicle adapted to the rails of railroad
	where passengers ride up and down
	the compartment that is suspended from an airship and that carries personnel and the cargo and the power plant
	a conveyance for passengers or freight on a cable railway