Breakdown of Wiem, że ona wyjechała za granicę.
ona
she / it (f)
wiedzieć
to know
że
that
za
behind; in (time)
Questions & Answers about Wiem, że ona wyjechała za granicę.
Why use wyjechała instead of pojechała?
Both refer to a completed trip by vehicle, but the prefix wy- specifically emphasizes departure. While pojechała just means she went to a destination, wyjechała stresses that she left her current place (often used for leaving town, going on a trip, or moving away).
How does za granicę mean "abroad"?
The word granica means "border". By combining it with the preposition za (behind/beyond), the phrase za granicę literally translates to "beyond the border".
Why does granicę end in -ę here instead of its dictionary form granica?
Because this sentence describes motion towards a destination, the preposition za takes the Accusative case (changing the feminine ending -a to -ę). If you wanted to say she is already living abroad (a fixed location instead of motion), you would use a different case: za granicą.
Is the comma before że mandatory?
Yes! Unlike in English where the comma is usually left out, in Polish you must always put a comma before the conjunction że (that) when it connects two parts of a sentence.