"'er" meaning in Dutch

{
  "head_templates": [
    {
      "args": {},
      "expansion": "'er",
      "name": "nl-adv"
    }
  ],
  "lang": "Dutch",
  "lang_code": "nl",
  "pos": "adv",
  "senses": [
    {
      "alt_of": [
        {
          "word": "der"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Dutch entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 3 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Abbreviation of der."
      ],
      "id": "en-'er-nl-adv-aXT4LjD3",
      "links": [
        [
          "der",
          "der#Dutch"
        ]
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ]
    }
  ],
  "word": "'er"
}

{
  "head_templates": [
    {
      "args": {},
      "expansion": "'er",
      "name": "nl-adv"
    }
  ],
  "lang": "Dutch",
  "lang_code": "nl",
  "pos": "adv",
  "senses": [
    {
      "alt_of": [
        {
          "word": "der"
        }
      ],
      "categories": [
        "Dutch abbreviations",
        "Dutch adverbs",
        "Dutch entries with incorrect language header",
        "Dutch lemmas",
        "Pages with 3 entries",
        "Pages with entries"
      ],
      "glosses": [
        "Abbreviation of der."
      ],
      "links": [
        [
          "der",
          "der#Dutch"
        ]
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ]
    }
  ],
  "word": "'er"
}