Kada ulaziš u zgradu, skreni levo; moj stan je tamo.

to be

Breakdown of Kada ulaziš u zgradu, skreni levo; moj stan je tamo.

• tamo: there
• moj: my
• stan: apartment

Questions & Answers about Kada ulaziš u zgradu, skreni levo; moj stan je tamo.

Why is it u zgradu and not u zgradi?

Because Serbian changes the case after u depending on whether you mean movement into something or location inside something.

• u zgradu = into the building → accusative
• u zgradi = in the building → locative

So in Kada ulaziš u zgradu, the idea is motion: you are going into the building.

A useful contrast:

• Ulaziš u zgradu. = You are entering the building.
• Ti si u zgradi. = You are in the building.

Why is it ulaziš?

Ulaziš is the 2nd person singular present tense of ulaziti / ulaziti-type verb ulaziti/ulaziti? More standardly, the verb is ulaziti = to be entering / to enter repeatedly / habitually, while the perfective partner is ući = to enter.

Here, ulaziš matches you in an informal singular sense: you enter / you are entering.

The ending -iš tells you it is:

• present tense
• 2nd person singular
• used with implied ti = you

So:

• ja ulazim = I enter / I am entering