"síns" meaning in Icelandic

{
  "head_templates": [
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      "args": {
        "1": "is",
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      "expansion": "síns",
      "name": "head"
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  ],
  "lang": "Icelandic",
  "lang_code": "is",
  "pos": "det",
  "senses": [
    {
      "categories": [
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          "kind": "other",
          "name": "Icelandic entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
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          "parents": [],
          "source": "w"
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      ],
      "examples": [
        {
          "english": "He borrowed his son's car.",
          "text": "Hann fékk lánaðan bíl sonar síns.",
          "type": "example"
        },
        {
          "english": "She accidentally took her husband's keys.",
          "text": "Hún tók óvart lykla manns síns.",
          "type": "example"
        }
      ],
      "form_of": [
        {
          "extra": "(“his/her(s)/its”)",
          "word": "sinn"
        }
      ],
      "glosses": [
        "genitive masculine/neuter singular of sinn (“his/her(s)/its”)"
      ],
      "id": "en-síns-is-det-jl9HIZSw",
      "links": [
        [
          "sinn",
          "sinn#Icelandic"
        ]
      ],
      "tags": [
        "form-of",
        "genitive",
        "masculine",
        "neuter",
        "singular"
      ]
    }
  ],
  "word": "síns"
}

{
  "head_templates": [
    {
      "args": {
        "1": "is",
        "2": "determiner form"
      },
      "expansion": "síns",
      "name": "head"
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  ],
  "lang": "Icelandic",
  "lang_code": "is",
  "pos": "det",
  "senses": [
    {
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        "Icelandic determiner forms",
        "Icelandic entries with incorrect language header",
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      ],
      "examples": [
        {
          "english": "He borrowed his son's car.",
          "text": "Hann fékk lánaðan bíl sonar síns.",
          "type": "example"
        },
        {
          "english": "She accidentally took her husband's keys.",
          "text": "Hún tók óvart lykla manns síns.",
          "type": "example"
        }
      ],
      "form_of": [
        {
          "extra": "(“his/her(s)/its”)",
          "word": "sinn"
        }
      ],
      "glosses": [
        "genitive masculine/neuter singular of sinn (“his/her(s)/its”)"
      ],
      "links": [
        [
          "sinn",
          "sinn#Icelandic"
        ]
      ],
      "tags": [
        "form-of",
        "genitive",
        "masculine",
        "neuter",
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  ],
  "word": "síns"
}