Breakdown of Wczoraj kupiliśmy nowy samochód.
samochód
car
nowy
new
wczoraj
yesterday
kupić
to buy (perfective)
Questions & Answers about Wczoraj kupiliśmy nowy samochód.
Why use kupiliśmy here instead of the imperfective form kupowaliśmy?
In Polish, we use the perfective aspect to talk about a single, finished action. Because buying the car was a completed event with a clear result, we use the perfective verb kupić rather than the imperfective kupować (which would mean we were in the process of buying or used to buy).
What does the -liśmy ending on kupiliśmy tell us about who is speaking?
The -śmy part means "we". The -li- part before it tells us the group included at least one man (the masculine personal form). If it was a group of only women, the verb would be kupiłyśmy.
Nowy samochód is the object being bought, so why didn't its ending change for the accusative case?
It actually is in the accusative case! For masculine inanimate nouns (objects like a car, house, or phone), the accusative form looks exactly the same as the basic dictionary form (nominative). That is why both the adjective nowy and the noun samochód look unchanged.
Why is there no Polish word for "we" (my) in this sentence?
Because the ending of the verb (kupiliśmy) already clearly means "we". Polish usually drops subject pronouns like ja, ty, or my unless you want to put special emphasis on them, such as saying "We bought it, not them."