Vocative Case / सम्बोधन विभक्ति (sambodhana vibhakti): Vocative Case or सम्बोधन विभक्ति (sambodhana vibhakti) of noun-form represents the word used to address or call someone or something. Study the following sentences. These are in vocative case.
All the above sentences address or call someone. So, the person or thing being addressed is in vocative case.