Imperfetto versus passato prossimo
Before we list the ways that the imperfetto and the passato prossimo are used differently, let’s look at a common construction in which they are used together:
To describe how one action was taking place (and continued to take place) when another action happened (and then finished):
Mentre leggevo il giornale lei ha preparato il caffè.
While I was reading [imperfect] the paper, she made [present perfect] the coffee.
Io dormivo quando lui è rientrato.
I was sleeping [imperfect] when he came back home [present perfect].
Mentre studiavano, lei è andata via.
While they were studying [imperfect], she left [present perfect].
The passato prossimo and the imperfetto have different uses to describe past events. Following are general guidelines for their respective purposes:
Passato prossimo
The passato prossimo is used to express a completed action in the past, e.g.,
Ieri ho pranzato con Silvia.
Yesterday I had lunch with Silvia.
The passato prossimo is used to express an action which happened once or a (stated) number of times, e.g.,
Giovedì siamo andati alla partita.
On Thursday we went to the game.
Siamo andati allo stadio tre volte.
We went to the stadium three times.
The passato prossimo is used to talk about events which occured in a sequence, e.g.,
Mi sono svegliato, ho preparato il caffè e ho letto il giornale.
I woke up, made the coffee, and read the paper.
The passato prossimo is used to describe an action concluded in a precise time frame:
Abbiamo aspettato cinque ore alla stazione.
We waited (for) five hours at the station.
Imperfetto
The imperfetto expresses a past action of indeterminate duration, e.g.,
In quel periodo, studiavo molto.
Back then I studied a lot.
The imperfetto describes a habitual action or an action which was regularly repeated, e.g.,
Facevamo colazione a quel bar.
We used to have breakfast at that cafe.
The imperfetto describes various events that were happening at the same time, e.g.,
Mentre studiavo, lei preparava la cena.
While I was studying, she was making dinner.
The imperfetto describes (clock) time in the past:
Erano le dieci quano sono rientrato
It was ten o’clock when I got back home