Questions & Answers about Przetańczyliśmy całą noc i jesteśmy wyczerpani.
Why is przetańczyliśmy perfective if it describes an ongoing action that lasted all night?
The prefix prze- is used here to mean doing an action continuously throughout a specific period. By adding it, the verb becomes perfective because it treats that entire duration of dancing as one single, successfully completed event.
Why do we use the accusative case for całą noc?
In Polish, expressing the duration of an action requires the accusative case. The accusative time expression całą noc pairs perfectly with the prze- prefix to emphasize that the dancing filled that exact, defined block of time.
Could I use the imperfective verb tańczyliśmy here instead?
Yes, but it changes the focus. Tańczyliśmy całą noc simply states what you were doing during the night. Using the prefixed perfective przetańczyliśmy strongly emphasizes the physical completion of the action across the whole time span, which sets up exactly why you are so exhausted.
Why does wyczerpani end in -ni?
It is the masculine personal (virile) plural form, which matches the subject implied by the -liśmy ending in przetańczyliśmy. If the group consisted only of women, the sentence would instead be Przetańczyłyśmy całą noc i jesteśmy wyczerpane.