Breakdown of Kiedy nie masz paszportu, nie możesz przekraczać tej granicy.
mieć
to have
nie
no / not
ten
this (m)
paszport
passport
Questions & Answers about Kiedy nie masz paszportu, nie możesz przekraczać tej granicy.
Why is the imperfective verb przekraczać used here instead of the perfective przekroczyć?
This highlights the core rule of negated modals. Using nie móc with an imperfective verb like przekraczać expresses a prohibition or a general rule: you are not allowed to cross. If we used the perfective przekroczyć, it would mean a physical inability to cross (for example, if a bridge was destroyed and you simply couldn't make it across).
Why is the border tej granicy (Genitive) instead of tę granicę (Accusative)? The verb przekraczać isn't directly negated!
The negation of a modal verb (nie możesz) carries over to the object of the infinitive. Since przekraczać normally requires the Accusative case, the negation at the start of the verb chain forces its direct object into the Genitive case. Because of this rule, tę granicę must become tej granicy.
Just as a refresher, why is paszportu in the Genitive case here?
This is the standard Genitive of Negation. The verb mieć (to have) takes the Accusative case in affirmative sentences (e.g., masz paszport), but when it is negated (nie masz), its direct object must change to the Genitive case (paszportu).
Could I use gdy instead of kiedy in this sentence?