"null anaphora" meaning in English

{
  "forms": [
    {
      "form": "null anaphoras",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "null anaphora (plural null anaphoras)",
      "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": "topical",
          "langcode": "en",
          "name": "Linguistics",
          "orig": "en:Linguistics",
          "parents": [
            "Language",
            "Social sciences",
            "Communication",
            "Sciences",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "2006, Natsuko Tsujimura, An Introduction to Japanese Linguistics",
          "text": "We have mentioned above that null anaphora is represented on syntactic trees as “pro”, and that this reflects the native speaker’s intuition that she or he somehow understands what is not overtly expressed and what the content of the null anaphora might be.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "An implied (but omitted) anaphora."
      ],
      "id": "en-null_anaphora-en-noun-zNr9UC94",
      "links": [
        [
          "linguistics",
          "linguistics"
        ]
      ],
      "raw_glosses": [
        "(linguistics) An implied (but omitted) anaphora."
      ],
      "topics": [
        "human-sciences",
        "linguistics",
        "sciences"
      ]
    }
  ],
  "word": "null anaphora"
}

{
  "forms": [
    {
      "form": "null anaphoras",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "null anaphora (plural null anaphoras)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with quotations",
        "Quotation templates to be cleaned",
        "en:Linguistics"
      ],
      "examples": [
        {
          "ref": "2006, Natsuko Tsujimura, An Introduction to Japanese Linguistics",
          "text": "We have mentioned above that null anaphora is represented on syntactic trees as “pro”, and that this reflects the native speaker’s intuition that she or he somehow understands what is not overtly expressed and what the content of the null anaphora might be.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "An implied (but omitted) anaphora."
      ],
      "links": [
        [
          "linguistics",
          "linguistics"
        ]
      ],
      "raw_glosses": [
        "(linguistics) An implied (but omitted) anaphora."
      ],
      "topics": [
        "human-sciences",
        "linguistics",
        "sciences"
      ]
    }
  ],
  "word": "null anaphora"
}