Learn German: Kennst du die Postleitzahl? - Do you know the postcode?

English uses "know" for everything, but German splits it. Wissen is used for knowing facts, usually followed by a clause or question word (like "I know what it is"). Kennen means to be acquainted or familiar with a specific noun (a person, place, or thing). Since you are asking about a specific noun (die Postleitzahl), you use kennen.

How do you break down the long compound word Postleitzahl?

It is made of three parts: Post (mail), the stem leit (from leiten, meaning to guide or route), and Zahl (number). It literally translates to "mail routing number".

Why is the article die used for Postleitzahl?

In German compound words, the gender is always determined by the very last noun in the chain. Since the word for number is feminine (die Zahl), the entire compound word takes the feminine article die.

What case is die Postleitzahl in this sentence?

It is in the accusative case because it is the direct object being acted upon by the verb kennen. For feminine nouns, the accusative article (die) looks exactly the same as the nominative (subject) article.