"Heawood conjecture" meaning in English

{
  "etymology_text": "Formulated in 1890 by Percy John Heawood.",
  "forms": [
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      "form": "the Heawood conjecture",
      "tags": [
        "canonical"
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  "lang": "English",
  "lang_code": "en",
  "pos": "name",
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          "name": "Graph theory",
          "orig": "en:Graph theory",
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      "glosses": [
        "A conjecture (proven in 1968) that gives a lower bound for the number of colors that are necessary for graph coloring on a surface of a given genus."
      ],
      "id": "en-Heawood_conjecture-en-name-R2fzIVGd",
      "links": [
        [
          "graph theory",
          "graph theory"
        ],
        [
          "surface",
          "surface"
        ],
        [
          "genus",
          "genus"
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      ],
      "raw_glosses": [
        "(graph theory) A conjecture (proven in 1968) that gives a lower bound for the number of colors that are necessary for graph coloring on a surface of a given genus."
      ],
      "related": [
        {
          "word": "Heawood number"
        },
        {
          "word": "Ringel-Youngs theorem"
        }
      ],
      "topics": [
        "graph-theory",
        "mathematics",
        "sciences"
      ]
    }
  ],
  "word": "Heawood conjecture"
}

{
  "etymology_text": "Formulated in 1890 by Percy John Heawood.",
  "forms": [
    {
      "form": "the Heawood conjecture",
      "tags": [
        "canonical"
      ]
    }
  ],
  "head_templates": [
    {
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        "def": "1"
      },
      "expansion": "the Heawood conjecture",
      "name": "en-prop"
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  "lang_code": "en",
  "pos": "name",
  "related": [
    {
      "word": "Heawood number"
    },
    {
      "word": "Ringel-Youngs theorem"
    }
  ],
  "senses": [
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        "en:Graph theory"
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      "glosses": [
        "A conjecture (proven in 1968) that gives a lower bound for the number of colors that are necessary for graph coloring on a surface of a given genus."
      ],
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        [
          "graph theory",
          "graph theory"
        ],
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          "surface",
          "surface"
        ],
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          "genus",
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        ]
      ],
      "raw_glosses": [
        "(graph theory) A conjecture (proven in 1968) that gives a lower bound for the number of colors that are necessary for graph coloring on a surface of a given genus."
      ],
      "topics": [
        "graph-theory",
        "mathematics",
        "sciences"
      ]
    }
  ],
  "word": "Heawood conjecture"
}