voc·a·tive 
(v
ŏk
ə-t
ĭv)
adj.1. Relating to, characteristic of, or used in calling.
2. Of, relating to, or being a grammatical case in certain inflected languages that indicates the person or thing being addressed.
n.1. The vocative case.
2. A word or form in the vocative case.
[Middle English vocatif, from Old French, from Latin vocātīvus (cāsus), vocative (case), from vocātus, past participle of vocāre, to call; see VOCATION.]
voca·tive·ly adv.