"4." meaning in Icelandic

{
  "head_templates": [
    {
      "args": {
        "1": "is",
        "2": "adjective"
      },
      "expansion": "4.",
      "name": "head"
    }
  ],
  "lang": "Icelandic",
  "lang_code": "is",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Icelandic entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "name": "Icelandic ordinal numbers",
          "parents": [
            "Ordinal numbers",
            "Numbers",
            "All topics",
            "Terms by semantic function",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 5 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "4th"
      ],
      "id": "en-4.-is-adj-E270QxxC",
      "links": [
        [
          "4th",
          "4th"
        ]
      ],
      "synonyms": [
        {
          "tags": [
            "masculine"
          ],
          "word": "fjórði"
        },
        {
          "tags": [
            "feminine",
            "neuter"
          ],
          "word": "fjórða"
        }
      ]
    }
  ],
  "word": "4."
}

{
  "head_templates": [
    {
      "args": {
        "1": "is",
        "2": "adjective"
      },
      "expansion": "4.",
      "name": "head"
    }
  ],
  "lang": "Icelandic",
  "lang_code": "is",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "Icelandic adjectives",
        "Icelandic entries with incorrect language header",
        "Icelandic lemmas",
        "Icelandic ordinal numbers",
        "Icelandic terms spelled with .",
        "Icelandic terms spelled with numbers",
        "Pages with 5 entries",
        "Pages with entries"
      ],
      "glosses": [
        "4th"
      ],
      "links": [
        [
          "4th",
          "4th"
        ]
      ]
    }
  ],
  "synonyms": [
    {
      "tags": [
        "masculine"
      ],
      "word": "fjórði"
    },
    {
      "tags": [
        "feminine",
        "neuter"
      ],
      "word": "fjórða"
    }
  ],
  "word": "4."
}

{
  "called_from": "linkages/371",
  "msg": "unrecognized linkage prefix: (4th): fjórði m, fjórða f or n desc=4th rest=fjórði m, fjórða f or n cls=romanization cls2=romanization e1=True e2=False",
  "path": [
    "4."
  ],
  "section": "Icelandic",
  "subsection": "adjective",
  "title": "4.",
  "trace": ""
}