"-∅" meaning in Translingual

{
  "head_templates": [
    {
      "args": {
        "1": "mul",
        "2": "suffix"
      },
      "expansion": "-∅",
      "name": "head"
    }
  ],
  "lang": "Translingual",
  "lang_code": "mul",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Translingual entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "mul",
          "name": "Linguistic morphology",
          "orig": "mul:Linguistic morphology",
          "parents": [
            "Linguistics",
            "Language",
            "Social sciences",
            "Communication",
            "Sciences",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Representation of the zero suffix."
      ],
      "id": "en--∅-mul-suffix-6RXzlJ8c",
      "links": [
        [
          "linguistic",
          "linguistic"
        ],
        [
          "morphology",
          "morphology"
        ],
        [
          "zero suffix",
          "zero suffix#English"
        ]
      ],
      "raw_glosses": [
        "(linguistic morphology) Representation of the zero suffix."
      ],
      "related": [
        {
          "word": "∅-"
        }
      ],
      "tags": [
        "morpheme"
      ],
      "topics": [
        "human-sciences",
        "linguistic-morphology",
        "linguistics",
        "morphology",
        "sciences"
      ]
    }
  ],
  "word": "-∅"
}

{
  "head_templates": [
    {
      "args": {
        "1": "mul",
        "2": "suffix"
      },
      "expansion": "-∅",
      "name": "head"
    }
  ],
  "lang": "Translingual",
  "lang_code": "mul",
  "pos": "suffix",
  "related": [
    {
      "word": "∅-"
    }
  ],
  "senses": [
    {
      "categories": [
        "Translingual entries with incorrect language header",
        "Translingual lemmas",
        "Translingual suffixes",
        "mul:Linguistic morphology"
      ],
      "glosses": [
        "Representation of the zero suffix."
      ],
      "links": [
        [
          "linguistic",
          "linguistic"
        ],
        [
          "morphology",
          "morphology"
        ],
        [
          "zero suffix",
          "zero suffix#English"
        ]
      ],
      "raw_glosses": [
        "(linguistic morphology) Representation of the zero suffix."
      ],
      "tags": [
        "morpheme"
      ],
      "topics": [
        "human-sciences",
        "linguistic-morphology",
        "linguistics",
        "morphology",
        "sciences"
      ]
    }
  ],
  "word": "-∅"
}