auto

In a sentence

• J'ai acheté une nouvelle auto.

  I bought a new car.

  In this sentence, 'auto' is used as a noun referring to a car, demonstrating its use as a synonym for 'voiture'.

• Elle est arrivée en auto, pas en vélo.

  She arrived by car, not by bike.

  Here, 'auto' is used to indicate the mode of transportation, referring to arriving via a car.

• Cette tâche est difficile, alors je l'accomplirai en auto-didacte.

  This task is difficult, so I will accomplish it as a self-taught person.

  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'.