"dü" meaning in Volapük

{
  "head_templates": [
    {
      "args": {
        "1": "vo",
        "2": "preposition"
      },
      "expansion": "dü",
      "name": "head"
    }
  ],
  "lang": "Volapük",
  "lang_code": "vo",
  "pos": "prep",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 9 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Volapük entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Volapük prepositions",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "english": "During his working life, he managed to find the time to study 88 different languages and dialects, and to play twelve musical instruments.",
          "ref": "1937, “‚Johann Martin Schleyer’”, in Volapükagased pro Nedänapükans, page 34:",
          "text": "Dü lif vobafulik oka ekanom tuvön timi ad studön pükis e dialegis 88 difikis, ed ad pläyön degtelati musigömas.",
          "type": "quote"
        }
      ],
      "glosses": [
        "during"
      ],
      "id": "en-dü-vo-prep-dmeOQM-L",
      "links": [
        [
          "during",
          "during"
        ]
      ]
    }
  ],
  "word": "dü"
}

{
  "head_templates": [
    {
      "args": {
        "1": "vo",
        "2": "preposition"
      },
      "expansion": "dü",
      "name": "head"
    }
  ],
  "lang": "Volapük",
  "lang_code": "vo",
  "pos": "prep",
  "senses": [
    {
      "categories": [
        "Pages with 9 entries",
        "Pages with entries",
        "Volapük entries with incorrect language header",
        "Volapük lemmas",
        "Volapük prepositions",
        "Volapük terms with quotations"
      ],
      "examples": [
        {
          "english": "During his working life, he managed to find the time to study 88 different languages and dialects, and to play twelve musical instruments.",
          "ref": "1937, “‚Johann Martin Schleyer’”, in Volapükagased pro Nedänapükans, page 34:",
          "text": "Dü lif vobafulik oka ekanom tuvön timi ad studön pükis e dialegis 88 difikis, ed ad pläyön degtelati musigömas.",
          "type": "quote"
        }
      ],
      "glosses": [
        "during"
      ],
      "links": [
        [
          "during",
          "during"
        ]
      ]
    }
  ],
  "word": "dü"
}