"księciu" meaning in Polish

{
  "head_templates": [
    {
      "args": {
        "1": "pl",
        "2": "noun form"
      },
      "expansion": "księciu",
      "name": "head"
    }
  ],
  "hyphenation": [
    "księ‧ciu"
  ],
  "lang": "Polish",
  "lang_code": "pl",
  "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": "Polish entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "form_of": [
        {
          "word": "książę"
        }
      ],
      "glosses": [
        "dative/locative singular of książę"
      ],
      "id": "en-księciu-pl-noun-1JW5jS4V",
      "links": [
        [
          "książę",
          "książę#Polish"
        ]
      ],
      "tags": [
        "dative",
        "form-of",
        "locative",
        "singular"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈkɕɛɲ.t͡ɕu/"
    },
    {
      "rhymes": "-ɛɲt͡ɕu"
    }
  ],
  "word": "księciu"
}

{
  "head_templates": [
    {
      "args": {
        "1": "pl",
        "2": "noun form"
      },
      "expansion": "księciu",
      "name": "head"
    }
  ],
  "hyphenation": [
    "księ‧ciu"
  ],
  "lang": "Polish",
  "lang_code": "pl",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Polish 2-syllable words",
        "Polish entries with incorrect language header",
        "Polish non-lemma forms",
        "Polish noun forms",
        "Polish terms with IPA pronunciation",
        "Rhymes:Polish/ɛɲt͡ɕu",
        "Rhymes:Polish/ɛɲt͡ɕu/2 syllables"
      ],
      "form_of": [
        {
          "word": "książę"
        }
      ],
      "glosses": [
        "dative/locative singular of książę"
      ],
      "links": [
        [
          "książę",
          "książę#Polish"
        ]
      ],
      "tags": [
        "dative",
        "form-of",
        "locative",
        "singular"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈkɕɛɲ.t͡ɕu/"
    },
    {
      "rhymes": "-ɛɲt͡ɕu"
    }
  ],
  "word": "księciu"
}