Expression du temps
French uses several different prepositions and constructions where English just says 'for', 'in', or 'since' — and they are NOT interchangeable. The big four are depuis (since / for, with an action still ongoing), pendant (during / for, with a finished action or general duration), pour (an intended duration looking forward, often future), and il y a (ago, looking back at a finished point). Layered on top, French has tense rules that don't match English: depuis + présent for what English does with the present perfect ('I have been waiting for an hour' = j'attends depuis une heure, present, not perfect). And there are two extremely useful periphrastic structures every B2+ speaker uses constantly: venir de + infinitif for 'just did' and être en train de + infinitif for 'right now in the middle of doing'.
depuis — since / for, action still ongoing
depuis answers the question 'from when until now', and crucially the verb is in the présent when the action is still going on (NOT the past, as in English). J'habite à Paris depuis cinq ans. = I have been living in Paris for five years. J'attends depuis une heure. = I have been waiting for an hour. Il pleut depuis ce matin. = It has been raining since this morning. Je le connais depuis 2010. = I have known him since 2010. The English present perfect ('have been V-ing') maps to French présent + depuis. With a negated or completed action, depuis can take the passé composé: Je ne l'ai pas vu depuis trois ans. = I haven't seen him in three years. With imparfait, depuis describes a state ongoing at a past reference point: J'habitais à Paris depuis cinq ans quand il est arrivé. = I had been living in Paris for five years when he arrived.
pendant — during, for (a completed or general duration)
pendant marks the duration during which an action takes place — closer to English 'during' or 'for' (in a finished sense). The verb tense is whatever the situation calls for; there's no special rule. J'ai habité à Paris pendant cinq ans. = I lived in Paris for five years (and I don't anymore). Pendant les vacances, j'ai beaucoup lu. = During the holidays, I read a lot. Il a parlé pendant deux heures. = He spoke for two hours. The contrast with depuis is sharp: Il pleut depuis trois jours (it has been raining for three days, still ongoing) vs. Il a plu pendant trois jours (it rained for three days, finished). pendant is also occasionally omitted before a duration in colloquial speech: J'ai travaillé deux heures. is fine.
pour — for (intended duration, future-looking)
pour + duration expresses the intended length of an action — typically about future plans, with verbs like partir, aller, venir, rester. Je pars en Italie pour deux semaines. = I'm leaving for Italy for two weeks. Il vient à Paris pour trois jours. = He's coming to Paris for three days. Elle est ici pour le week-end. = She's here for the weekend. The key feature: the duration is the plan, not what has already happened. With past time, you usually want pendant, not pour: J'ai habité à Paris pendant cinq ans (I lived there for five years), NOT pour cinq ans. (Beware: pour with past = 'for the purpose of', a different meaning.) Some learners think pour is the natural translation of English 'for' — it's not; pendant is more common.
il y a — ago (a single point in the past)
il y a + duration = 'X ago' — a single point of time before now. The verb is normally in the passé composé. Je suis arrivé il y a deux heures. = I arrived two hours ago. Elle est partie il y a trois jours. = She left three days ago. Il y a longtemps, je vivais en Espagne. = A long time ago, I lived in Spain. Note: this is the same il y a as in il y a un livre sur la table ('there is a book on the table') — the construction is identical, the meaning is contextual. Don't confuse il y a + duration ('ago') with depuis + duration ('for'): il y a trois jours = three days ago; depuis trois jours = for three days now. Quick test: 'ago' = single moment in past = il y a; 'for/since' = ongoing duration = depuis.
dans and en — within / in, for the future
Two more, often confused. dans + duration = 'in X time / X from now' — at the END of that period. Je partirai dans une heure. = I'll leave in an hour (i.e., one hour from now). Le train arrive dans dix minutes. = The train arrives in ten minutes. dans deux ans, je vais terminer mes études. = In two years, I'll finish my studies. en + duration = 'within / in the span of' — how long the action TAKES. Je finirai en une heure. = I'll finish within an hour (the work takes an hour). Il a fait ses devoirs en vingt minutes. = He did his homework in twenty minutes (it took 20 min). The English 'in two hours' is ambiguous; French disambiguates: dans deux heures (starting in two hours) vs. en deux heures (it takes two hours).
ça fait... que / voilà... que
Two periphrastic equivalents of depuis that emphasize the duration. Ça fait + duration + que + clause = 'It's been X amount of time that...'. Ça fait cinq ans que j'habite à Paris. = It's been five years that I've been living in Paris. = I've been living in Paris for five years. Ça fait une heure que j'attends. = It's been an hour that I've been waiting. Voilà + duration + que + clause is the same idea, slightly more formal/literary: Voilà trois jours qu'il pleut. = It has been raining for three days. Voilà longtemps qu'on ne s'est pas vus! = It's been a long time since we've seen each other! These three structures (depuis, ça fait... que, voilà... que) are roughly interchangeable, but ça fait... que is the most common in everyday speech.
venir de + infinitif — the immediate past
venir de + infinitif literally 'to come from doing' = just did, the immediate past. This is one of the most useful structures in French — there's no good single-word English equivalent. Je viens d'arriver. = I just arrived. Elle vient de partir. = She just left. Nous venons de manger. = We just ate. Il vient de me téléphoner. = He just called me. With the imparfait of venir, you get 'had just done': Il venait de partir quand je suis arrivé. = He had just left when I arrived. Critical detail: the action must be very recent — typically within minutes. For 'I read it last week', you'd say je l'ai lu la semaine dernière, NOT je viens de le lire. Pronouns go before the infinitif: Je viens de le voir. = I just saw him.
être en train de + infinitif — right now, in the middle of
French doesn't have a present continuous tense — je mange can mean both 'I eat' and 'I am eating'. When you really need to emphasize that something is happening at this very moment, use être en train de + infinitif = 'to be in the process of doing'. Je suis en train de manger. = I'm (right now) eating. Elle est en train de travailler — ne la dérange pas. = She's working right now — don't bother her. Nous étions en train de discuter quand le téléphone a sonné. = We were in the middle of discussing when the phone rang. The construction works in any tense: j'étais en train de (imparfait), je serai en train de (futur). Use it sparingly — for everyday 'I'm doing X', the simple présent is fine. Use en train de for emphasis or when ambiguity matters.
Quick recap
(1) depuis + présent = 'for/since', still ongoing — replaces English present perfect. (2) pendant = 'for/during', any tense, often finished. (3) pour + duration = future-intended length (je pars pour deux semaines). (4) il y a + duration = 'ago' (with passé composé). (5) dans + duration = 'in X time' (future point); en + duration = 'within X' (how long it takes). (6) ça fait... que = colloquial depuis; voilà... que = literary version. (7) venir de + INF = just did. (8) être en train de + INF = right now, mid-action.
