"yr undydd" meaning in Welsh

{
  "etymology_text": "yr (“the”) + undydd (“one day”).",
  "head_templates": [
    {
      "args": {
        "1": "m",
        "2": "-"
      },
      "expansion": "yr undydd m (uncountable)",
      "name": "cy-noun"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "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": "Welsh entries with incorrect language header",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Welsh links with redundant wikilinks",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "cy",
          "name": "Time",
          "orig": "cy:Time",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "the same day"
      ],
      "id": "en-yr_undydd-cy-noun-Y1GcrTCa",
      "links": [
        [
          "same",
          "same"
        ],
        [
          "day",
          "day"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) the same day"
      ],
      "related": [
        {
          "english": "the same night",
          "word": "yr unnos"
        }
      ],
      "tags": [
        "idiomatic",
        "masculine",
        "uncountable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/əˈrɨ̞ndɨ̞ð/",
      "tags": [
        "North-Wales"
      ]
    },
    {
      "ipa": "/əˈrɪndɪð/",
      "tags": [
        "South-Wales"
      ]
    },
    {
      "rhymes": "-ɨ̞ndɨ̞ð"
    }
  ],
  "word": "yr undydd"
}

{
  "etymology_text": "yr (“the”) + undydd (“one day”).",
  "head_templates": [
    {
      "args": {
        "1": "m",
        "2": "-"
      },
      "expansion": "yr undydd m (uncountable)",
      "name": "cy-noun"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "noun",
  "related": [
    {
      "english": "the same night",
      "word": "yr unnos"
    }
  ],
  "senses": [
    {
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Rhymes:Welsh/ɨ̞ndɨ̞ð",
        "Rhymes:Welsh/ɨ̞ndɨ̞ð/3 syllables",
        "Welsh entries with incorrect language header",
        "Welsh idioms",
        "Welsh lemmas",
        "Welsh links with redundant wikilinks",
        "Welsh masculine nouns",
        "Welsh multiword terms",
        "Welsh nouns",
        "Welsh uncountable nouns",
        "cy:Time"
      ],
      "glosses": [
        "the same day"
      ],
      "links": [
        [
          "same",
          "same"
        ],
        [
          "day",
          "day"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) the same day"
      ],
      "tags": [
        "idiomatic",
        "masculine",
        "uncountable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/əˈrɨ̞ndɨ̞ð/",
      "tags": [
        "North-Wales"
      ]
    },
    {
      "ipa": "/əˈrɪndɪð/",
      "tags": [
        "South-Wales"
      ]
    },
    {
      "rhymes": "-ɨ̞ndɨ̞ð"
    }
  ],
  "word": "yr undydd"
}