electric car vs auto

electric car and auto both are nouns.

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

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

electric car: a car that is powered by electricity
auto: a motor vehicle with four wheels; usually propelled by an internal combustion engine

Other hypernyms of electric car include automobile, car, machine, motorcar.

electric car (noun)	auto (noun)
a car that is powered by electricity	a motor vehicle with four wheels; usually propelled by an internal combustion engine