When you wish to address a person, you cannot just state their name. Lithuanians have a special case for greeting. This is how you should greet Vytautas, Laimis, Kazys and Darius:

Labas, Vytautai!
Sveikas, Laimi!
Labas, Kazy!
Sveikas, Dariau!

As you see, the endings have changed. The name of this new case is vocative or šauksmininkas. It's the same when you state a person's name in order to get their attention:

Vytautai, atleisk! (Vytautas, forgive me!)
Laimi, kiek valandų? (Laimis, what time is it?)
Kazy, Dariau, kur jūs? (Kazys, Darius, where are you?)