"I Can't": Aspect Matters
In English, "I can't bring this" could mean it is against the rules (prohibition) or physically too heavy (inability). In Polish, when you negate a modal verb like móc (to be able to), the aspect of the main verb determines the exact meaning.
Prohibition and General Rules (Imperfective)
To state a rule or prohibition ("you must not"), use nie móc + an imperfective verb. This emphasizes the general, ongoing nature of the restriction.
| to bring in (carry inside, imperfective) | wnosić |
| In accordance with aviation regulations, you cannot bring liquids on board. | Zgodnie z regulaminem lotniczym nie możesz wnosić płynów na pokład. |
| Your carry-on luggage cannot exceed the weight limit. | Twój bagaż podręczny nie może przekraczać limitu wagi. |
Similarly, to express general reluctance or refusal, pair nie chcieć (not to want) with an imperfective verb.
| Passengers do not want to bring heavy items on board. | Pasażerowie nie chcą wnosić ciężkich przedmiotów na pokład. |
Physical Inability (Perfective)
To express physical inability on a specific occasion ("I couldn't manage to do it"), use nie móc + a perfective verb. This highlights a single attempt that failed or physically could not be completed.
| to bring in (carry inside, perfective) | wnieść |
| After check-in, I couldn't bring this bag in because it was too heavy. | Po odprawie nie mogłem wnieść tej torby, bo była zbyt ciężka. |
| to exceed (perfective) | przekroczyć |
| I couldn't cross the border because I had a strange item in my backpack. | Nie mogłem przekroczyć granicy, bo miałem w plecaku dziwny przedmiot. |
Side-by-Side Comparison
Let's look at the verbs for crossing a border: przekraczać (imperfective) and przekroczyć (perfective).
If someone tried to cross on a specific occasion but was turned away, it is an inability to complete the action. We use the perfective:
| The man could not cross the border without a passport. | Mężczyzna nie mógł przekroczyć granicy bez paszportu. |
However, if we are stating the general rule that crossing without a passport is forbidden, it is a strict prohibition. We use the imperfective:
| When you do not have a passport, you cannot cross this border. | Kiedy nie masz paszportu, nie możesz przekraczać tej granicy. |