French Grammar: French Preposition (depuis)

Definition: To express the duration of an event in French, depuis and pendant are used. Many English speakers tend to translate for as pour, but this is rarely correct when talking about time.

Depuis means since or for. It is used with a verb in the present tense to talk about an action that began in the past and continues in the present.

Depuis quand étudiez-vous le français?
How long have you studied French?

J'étudie le français depuis 6 ans.
I've studied French for 6 years.

J'étudie le français depuis 2000.
I've studied French since 2000.

Depuis can also be used to indicate an action that was occuring (in the imparfait) when it was interrupted by another action (in the passé composé).

Depuis quand dormais-tu quand je suis arrivé ?
How long had you been sleeping when I arrived?

Pendant means for, but it refers to an action in its entirety that has no relation to the present.
It can be used for both the past and the future.

Pendant combien de temps avez-vous étudié le français ?
How long did you study French?

J'ai étudié le français pendant 3 ans.
I studied French for 3 years.

Je vais habiter en France pendant 2 mois.
I'm going to live in France for 2 months.

Pendant also means during.

J'ai vu un film pendant mon séjour.
I saw a film during my stay.

Pendant ce temps, il m'attendait.
During this time, he waited for me.