"dummy subject" meaning in English

{
  "forms": [
    {
      "form": "dummy subjects",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "dummy subject (plural dummy subjects)",
      "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": "Entries with translation boxes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Dutch translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Grammar",
          "orig": "en:Grammar",
          "parents": [
            "Linguistics",
            "Language",
            "Social sciences",
            "Communication",
            "Sciences",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "In the expression \"It's raining\", the word \"it\" is a dummy subject.",
          "type": "example"
        }
      ],
      "glosses": [
        "A word (in English, it or there) used as the subject of a sentence when the real subject is placed after the main verb, or when the subject is indefinite."
      ],
      "id": "en-dummy_subject-en-noun-zfcijN-k",
      "links": [
        [
          "grammar",
          "grammar"
        ],
        [
          "word",
          "word"
        ],
        [
          "subject",
          "subject"
        ],
        [
          "sentence",
          "sentence"
        ],
        [
          "verb",
          "verb"
        ]
      ],
      "raw_glosses": [
        "(grammar) A word (in English, it or there) used as the subject of a sentence when the real subject is placed after the main verb, or when the subject is indefinite."
      ],
      "synonyms": [
        {
          "word": "introductory subject"
        },
        {
          "word": "preparatory subject"
        }
      ],
      "topics": [
        "grammar",
        "human-sciences",
        "linguistics",
        "sciences"
      ],
      "translations": [
        {
          "code": "nl",
          "lang": "Dutch",
          "sense": "grammatical subject carrying no meaning of its own",
          "tags": [
            "neuter"
          ],
          "word": "loos onderwerp"
        }
      ]
    }
  ],
  "word": "dummy subject"
}

{
  "forms": [
    {
      "form": "dummy subjects",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "dummy subject (plural dummy subjects)",
      "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 usage examples",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Terms with Dutch translations",
        "en:Grammar"
      ],
      "examples": [
        {
          "text": "In the expression \"It's raining\", the word \"it\" is a dummy subject.",
          "type": "example"
        }
      ],
      "glosses": [
        "A word (in English, it or there) used as the subject of a sentence when the real subject is placed after the main verb, or when the subject is indefinite."
      ],
      "links": [
        [
          "grammar",
          "grammar"
        ],
        [
          "word",
          "word"
        ],
        [
          "subject",
          "subject"
        ],
        [
          "sentence",
          "sentence"
        ],
        [
          "verb",
          "verb"
        ]
      ],
      "raw_glosses": [
        "(grammar) A word (in English, it or there) used as the subject of a sentence when the real subject is placed after the main verb, or when the subject is indefinite."
      ],
      "topics": [
        "grammar",
        "human-sciences",
        "linguistics",
        "sciences"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "introductory subject"
    },
    {
      "word": "preparatory subject"
    }
  ],
  "translations": [
    {
      "code": "nl",
      "lang": "Dutch",
      "sense": "grammatical subject carrying no meaning of its own",
      "tags": [
        "neuter"
      ],
      "word": "loos onderwerp"
    }
  ],
  "word": "dummy subject"
}