Vocative case

The vocative case (abbreviated VOC, voc.) is the case used for a noun that identifies a person (animal, object, etc.) being addressed or, occasionally, the determiners of that noun. A vocative expression is an expression of direct address where the identity of the party spoken to is set forth expressly within a sentence. For example, in the sentence, ""I don't know, John"", John is a vocative expression that indicates the party being addressed—as opposed to the sentence, ""I don't know John"", where John is the direct object of the verb ""know.""Historically, the vocative case was an element of the Indo-European system of cases, and existed in Latin, Sanskrit, and Classical Greek. Many modern Indo-European languages have lost the vocative case. Many, however, retain it, including the Baltic languages and most Slavic languages.Some linguists argue that the vocative form is not a case but a special form of nouns not belonging to any case, since vocative expressions are not related syntactically to other words in sentences.