wiesz

In a sentence

• Wiesz, że jesteś bardzo uzdolniony?

  Do you know that you are very talented?

  Here, 'wiesz' is used to mean 'you know', acting as a verb to address the person's knowledge of a fact.

• Wiesz, gdzie się podziały moje klucze?

  Do you know where my keys have gone?

  In this sentence, 'wiesz' is also a verb meaning 'you know', asking about the person's knowledge of the location of an object.

• Ale wiesz, że to może być trudne?

  But you know that it might be difficult?

  Here, 'wiesz' implies assurance or emphasizing the importance of recognizing a fact.