"llengua materna" meaning in Catalan

{
  "forms": [
    {
      "form": "llengües maternes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f"
      },
      "expansion": "llengua materna f (plural llengües maternes)",
      "name": "ca-noun"
    }
  ],
  "lang": "Catalan",
  "lang_code": "ca",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Catalan entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "ca",
          "name": "Language",
          "orig": "ca:Language",
          "parents": [
            "Communication",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "mother tongue"
      ],
      "id": "en-llengua_materna-ca-noun-eUb2gChl",
      "links": [
        [
          "mother tongue",
          "mother tongue"
        ]
      ],
      "tags": [
        "feminine"
      ]
    }
  ],
  "word": "llengua materna"
}

{
  "forms": [
    {
      "form": "llengües maternes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f"
      },
      "expansion": "llengua materna f (plural llengües maternes)",
      "name": "ca-noun"
    }
  ],
  "lang": "Catalan",
  "lang_code": "ca",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Catalan countable nouns",
        "Catalan entries with incorrect language header",
        "Catalan feminine nouns",
        "Catalan lemmas",
        "Catalan multiword terms",
        "Catalan nouns",
        "ca:Language"
      ],
      "glosses": [
        "mother tongue"
      ],
      "links": [
        [
          "mother tongue",
          "mother tongue"
        ]
      ],
      "tags": [
        "feminine"
      ]
    }
  ],
  "word": "llengua materna"
}