"fille unique" meaning in French

{
  "forms": [
    {
      "form": "filles uniques",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f"
      },
      "expansion": "fille unique f (plural filles uniques)",
      "name": "fr-noun"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "French entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "fr",
          "name": "Family",
          "orig": "fr:Family",
          "parents": [
            "People",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "fr",
          "name": "Female family members",
          "orig": "fr:Female family members",
          "parents": [
            "Family members",
            "Female people",
            "Family",
            "Female",
            "People",
            "Gender",
            "Human",
            "Biology",
            "Psychology",
            "Sociology",
            "All topics",
            "Sciences",
            "Social sciences",
            "Fundamental",
            "Society"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Female only child"
      ],
      "id": "en-fille_unique-fr-noun-K9ux6nn9",
      "links": [
        [
          "only child",
          "only child"
        ]
      ],
      "related": [
        {
          "word": "fils unique"
        }
      ],
      "tags": [
        "feminine"
      ]
    }
  ],
  "word": "fille unique"
}

{
  "forms": [
    {
      "form": "filles uniques",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f"
      },
      "expansion": "fille unique f (plural filles uniques)",
      "name": "fr-noun"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "noun",
  "related": [
    {
      "word": "fils unique"
    }
  ],
  "senses": [
    {
      "categories": [
        "French countable nouns",
        "French entries with incorrect language header",
        "French feminine nouns",
        "French lemmas",
        "French multiword terms",
        "French nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "fr:Family",
        "fr:Female family members"
      ],
      "glosses": [
        "Female only child"
      ],
      "links": [
        [
          "only child",
          "only child"
        ]
      ],
      "tags": [
        "feminine"
      ]
    }
  ],
  "word": "fille unique"
}