The
vocative case (
abbreviated , 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."