Breakdown of Passeggiavamo tranquilli quando improvvisamente ha iniziato a piovere.
tranquillo
quiet
quando
when
iniziare
to start
a
to / at
Questions & Answers about Passeggiavamo tranquilli quando improvvisamente ha iniziato a piovere.
Why do we use the imperfetto for passeggiavamo but the passato prossimo for ha iniziato?
This is the classic way to tell a story in Italian! Use the imperfetto (passeggiavamo) for the ongoing background action, and the passato prossimo (ha iniziato) for the sudden event that interrupts it. The word quando (when) usually introduces that interrupting event.
Could we swap quando for mentre in this sentence?
Not in the exact same spot. Mentre means 'while' and must be followed by the ongoing background action in the imperfetto. You would have to flip the structure to keep the meaning: Mentre passeggiavamo tranquilli, improvvisamente ha iniziato a piovere (While we were strolling peacefully, it suddenly started to rain).
Since 'peacefully' is an adverb in English, why does Italian use the adjective tranquilli?
Why is there an 'a' between ha iniziato and piovere?
The verb iniziare (to start) requires the preposition a before a following infinitive verb. Whenever you want to say 'to start doing something' in Italian, the pattern is iniziare a + infinitive.