Vocative /(?)/

Voc·a·tive

Vocative

a.
  1. Of or pertaining to calling; used in calling; specifically (Gram.), used in address; appellative; -- said of that case or form of the noun, pronoun, or adjective, in which a person or thing is addressed; as, Domine, O Lord. (Gram.)

Vocative

n.
  1. The vocative case. (Gram.)