"underdensity" meaning in English

{
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    {
      "args": {
        "1": "en",
        "2": "under",
        "3": "density"
      },
      "expansion": "under- + density",
      "name": "prefix"
    }
  ],
  "etymology_text": "under- + density",
  "forms": [
    {
      "form": "underdensities",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "underdensity (plural underdensities)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms prefixed with under-",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "2015, Stephanie Tonnesen, Renyue Cen, “Don't Forget the Forest for the Trees: The Stellar-Mass Halo-Mass Relation in Different Environments”, in arXiv",
          "text": "In this paper we use high-resolution hydrodynamical cosmological simulations to compare the halo and stellar mass growth of galaxies in a large-scale overdensity to those in a large-scale underdensity (on scales of about 20 Mpc).",
          "type": "quotation"
        }
      ],
      "glosses": [
        "The condition or extent of being underdense."
      ],
      "id": "en-underdensity-en-noun-1xXtYa4S",
      "links": [
        [
          "underdense",
          "underdense"
        ]
      ]
    }
  ],
  "word": "underdensity"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "under",
        "3": "density"
      },
      "expansion": "under- + density",
      "name": "prefix"
    }
  ],
  "etymology_text": "under- + density",
  "forms": [
    {
      "form": "underdensities",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "underdensity (plural underdensities)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English terms prefixed with under-",
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      ],
      "examples": [
        {
          "ref": "2015, Stephanie Tonnesen, Renyue Cen, “Don't Forget the Forest for the Trees: The Stellar-Mass Halo-Mass Relation in Different Environments”, in arXiv",
          "text": "In this paper we use high-resolution hydrodynamical cosmological simulations to compare the halo and stellar mass growth of galaxies in a large-scale overdensity to those in a large-scale underdensity (on scales of about 20 Mpc).",
          "type": "quotation"
        }
      ],
      "glosses": [
        "The condition or extent of being underdense."
      ],
      "links": [
        [
          "underdense",
          "underdense"
        ]
      ]
    }
  ],
  "word": "underdensity"
}