"Markovnikov's rule" meaning in English

{
  "etymology_text": "The rule was formulated by the Russian chemist Vladimir Vasilevich Markovnikov in 1870.",
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  "lang_code": "en",
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          "name": "Organic chemistry",
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            "Fundamental"
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      "glosses": [
        "A rule describing the outcome of certain addition reactions in organic chemistry."
      ],
      "id": "en-Markovnikov's_rule-en-name-3-QzBdXG",
      "links": [
        [
          "organic chemistry",
          "organic chemistry"
        ],
        [
          "addition reaction",
          "addition reaction"
        ]
      ],
      "raw_glosses": [
        "(organic chemistry) A rule describing the outcome of certain addition reactions in organic chemistry."
      ],
      "related": [
        {
          "word": "anti-Markovnikov"
        }
      ],
      "synonyms": [
        {
          "word": "Markovnikov rule"
        },
        {
          "word": "Markownikoff's rule"
        }
      ],
      "topics": [
        "chemistry",
        "natural-sciences",
        "organic-chemistry",
        "physical-sciences"
      ]
    }
  ],
  "word": "Markovnikov's rule"
}

{
  "etymology_text": "The rule was formulated by the Russian chemist Vladimir Vasilevich Markovnikov in 1870.",
  "head_templates": [
    {
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      "expansion": "Markovnikov's rule",
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  "lang": "English",
  "lang_code": "en",
  "pos": "name",
  "related": [
    {
      "word": "anti-Markovnikov"
    }
  ],
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        "en:Chemical reactions",
        "en:Organic chemistry"
      ],
      "glosses": [
        "A rule describing the outcome of certain addition reactions in organic chemistry."
      ],
      "links": [
        [
          "organic chemistry",
          "organic chemistry"
        ],
        [
          "addition reaction",
          "addition reaction"
        ]
      ],
      "raw_glosses": [
        "(organic chemistry) A rule describing the outcome of certain addition reactions in organic chemistry."
      ],
      "topics": [
        "chemistry",
        "natural-sciences",
        "organic-chemistry",
        "physical-sciences"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "Markovnikov rule"
    },
    {
      "word": "Markownikoff's rule"
    }
  ],
  "word": "Markovnikov's rule"
}