"caso vocativo" meaning in Spanish

{
  "forms": [
    {
      "form": "casos vocativos",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "m"
      },
      "expansion": "caso vocativo m (plural casos vocativos)",
      "name": "es-noun"
    }
  ],
  "lang": "Spanish",
  "lang_code": "es",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Spanish entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "es",
          "name": "Grammatical cases",
          "orig": "es:Grammatical cases",
          "parents": [
            "Grammar",
            "Linguistics",
            "Language",
            "Social sciences",
            "Communication",
            "Sciences",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "vocative case"
      ],
      "id": "en-caso_vocativo-es-noun-wdJkD~bN",
      "links": [
        [
          "grammar",
          "grammar"
        ],
        [
          "vocative case",
          "vocative case"
        ]
      ],
      "raw_glosses": [
        "(grammar) vocative case"
      ],
      "tags": [
        "masculine"
      ],
      "topics": [
        "grammar",
        "human-sciences",
        "linguistics",
        "sciences"
      ],
      "wikipedia": [
        "es:caso vocativo"
      ]
    }
  ],
  "word": "caso vocativo"
}

{
  "forms": [
    {
      "form": "casos vocativos",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "m"
      },
      "expansion": "caso vocativo m (plural casos vocativos)",
      "name": "es-noun"
    }
  ],
  "lang": "Spanish",
  "lang_code": "es",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Spanish countable nouns",
        "Spanish entries with incorrect language header",
        "Spanish lemmas",
        "Spanish masculine nouns",
        "Spanish multiword terms",
        "Spanish nouns",
        "es:Grammatical cases"
      ],
      "glosses": [
        "vocative case"
      ],
      "links": [
        [
          "grammar",
          "grammar"
        ],
        [
          "vocative case",
          "vocative case"
        ]
      ],
      "raw_glosses": [
        "(grammar) vocative case"
      ],
      "tags": [
        "masculine"
      ],
      "topics": [
        "grammar",
        "human-sciences",
        "linguistics",
        "sciences"
      ],
      "wikipedia": [
        "es:caso vocativo"
      ]
    }
  ],
  "word": "caso vocativo"
}