This is the 8695th most frequent French word.
auto
"Auto" in French means "car" or "automobile" in English.
In this sentence, 'auto' is used as a noun referring to a car, demonstrating its use as a synonym for 'voiture'.
J'ai acheté une nouvelle auto.
I bought a new car.
Here, 'auto' is used to indicate the mode of transportation, referring to arriving via a car.
Elle est arrivée en auto, pas en vélo.
She arrived by car, not by bike.
In this context, 'auto' is part of the word 'auto-didacte', describing the concept of self-teaching, showing its use as a prefix meaning 'self'.