This is the 746th most frequent Polish word.
zna
"Zna" means "knows" (third person singular).
The word 'zna' is a verb indicating a state of knowledge or awareness.
Anna zna odpowiedź na to pytanie.
Anna knows the answer to this question.
Here, 'zna' signifies a personal acquaintance with someone.
Marek zna swoją sąsiadkę od lat.
Marek has known his neighbor for years.
In this question format, 'zna' is used to ask about recognizing or identifying someone.