par
by (introducing the agent, author or maker, especially in passive constructions)
Ce roman a été écrit par Marguerite.
This novel was written by Marguerite.
by, via, through (indicating means, channel or route)
J'envoie le colis par la poste.
I send the parcel by mail.
per, each (indicating rate, frequency or distribution)
Je vais à la salle trois fois par semaine.
I go to the gym three times a week.
one by one, successively (indicating order or succession)
Ils ont répondu aux questions un par un.
They answered the questions one by one.
Notes
GENERAL INFO
Par is a preposition. It primarily means "by," "through," "per," or "for," depending on context. It indicates agent, means, movement, or distribution.
USAGE
Par commonly introduces the agent in passive sentences (*écrit par*) or indicates the means (*envoyer par la poste*). It also expresses frequency (*deux fois par semaine*) or movement through a place (*passer par ici*).
TRAPS
Don't confuse par with "pour." While both can mean "for," par implies means/agent (e.g., *payer par carte* - pay by card), whereas "pour" signifies purpose or destination (e.g., *payer pour le café* - pay for the coffee). For travel, "by car" is usually *en voiture*, not *par voiture*.
