(n) :
case of address, case used for a noun identifying the person or thing being addressed. It corresponds to English "O" as used in solemn or poetic address: Hear me, O Albion! Languages that regularly employ the vocative include
Arabic,
Croatian,
Czech,
Greek,
Hawaiian,
Hindi,
Latin,
Lithuanian,
Ojibwe,
Polish,
Romanian,
Sanskrit, and
Serbian