arrêter
to stop (an action, movement or process)
to quit (a habit)
to turn off (a machine, a light)
Il faut arrêter de fumer.
You need to quit smoking.
to arrest (by the police)
to detain
La police a décidé d'arrêter le suspect devant chez lui.
The police decided to arrest the suspect in front of his house.
to decide on or to set (a date, a price, a plan)
Nous avons arrêté la date du rendez-vous.
We set the date of the appointment.
to stop (intransitive, often reflexive: to come to a halt)
Le bus va s'arrêter devant l'école.
The bus is going to stop in front of the school.
Notes
GENERAL INFO
Arrêter is a regular -ER verb meaning "to stop" (an action, an object, or oneself) or "to arrest."
USAGE
It is used transitively (`arrêter la voiture` - to stop the car), reflexively (`s'arrêter` - to stop oneself/come to a stop), and with `de` + infinitive (`arrêter de fumer` - to stop smoking).
TRAPS
While arrêter can mean "to arrest," its most common use is "to stop."
Do not confuse "arrêter de" (to stop doing something) with s'arrêter (for a person/thing to stop moving).
CONJUGATION - 1st Group
J'arrête
Tu arrêtes
Il/elle/on arrête
nous arrêtons
Vous arrêtez
Ils/elles arrêtent
