"Em" meaning in Conventions internationales

{
  "categories": [
    {
      "kind": "other",
      "name": "Symboles désuets des éléments chimiques",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Symboles en conventions internationales",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Conventions internationales",
      "orig": "conventions internationales",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Conventions internationales",
  "lang_code": "conv",
  "pos": "symbol",
  "pos_title": "Symbole",
  "related": [
    {
      "sense": "Examètre (1) :",
      "word": "m"
    }
  ],
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Lexique en conventions internationales de la métrologie",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Symbole de l’examètre, unité de mesure de longueur du Système international (SI), valant 1 000 000 000 000 000 000 mètres (10¹⁸ mètres)."
      ],
      "id": "fr-Em-conv-symbol-WalHUCQq",
      "topics": [
        "metrology"
      ]
    },
    {
      "glosses": [
        "Symbole de l’élément chimique « émanation », maintenant appelé radon (Rn)."
      ],
      "id": "fr-Em-conv-symbol-~uOX-Ug-",
      "tags": [
        "obsolete"
      ],
      "topics": [
        "chemistry"
      ]
    },
    {
      "glosses": [
        "Symbole de l’élément chimique « émanium », maintenant appelé actinium (Ac)."
      ],
      "id": "fr-Em-conv-symbol-OobOpKDa",
      "tags": [
        "obsolete"
      ],
      "topics": [
        "chemistry"
      ]
    },
    {
      "categories": [
        {
          "kind": "other",
          "name": "Lexique en conventions internationales de la chimie",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Symbole chimique de l’éka-manganèse, élément prédit par Dmitri Mendeleïev en 1871  . En 1937, il est remplacé par le technétium (Tc)."
      ],
      "id": "fr-Em-conv-symbol-gv58nTXo",
      "tags": [
        "obsolete"
      ],
      "topics": [
        "chemistry"
      ]
    }
  ],
  "synonyms": [
    {
      "sense": "Émanation (2) :",
      "word": "Rn"
    },
    {
      "sense": "Émanation (3) :",
      "word": "Ac"
    },
    {
      "sense": "Éka-manganèse (4) :",
      "word": "Tc"
    }
  ],
  "tags": [
    "invariable"
  ],
  "word": "Em"
}

{
  "categories": [
    "Symboles désuets des éléments chimiques",
    "Symboles en conventions internationales",
    "conventions internationales"
  ],
  "lang": "Conventions internationales",
  "lang_code": "conv",
  "pos": "symbol",
  "pos_title": "Symbole",
  "related": [
    {
      "sense": "Examètre (1) :",
      "word": "m"
    }
  ],
  "senses": [
    {
      "categories": [
        "Lexique en conventions internationales de la métrologie"
      ],
      "glosses": [
        "Symbole de l’examètre, unité de mesure de longueur du Système international (SI), valant 1 000 000 000 000 000 000 mètres (10¹⁸ mètres)."
      ],
      "topics": [
        "metrology"
      ]
    },
    {
      "glosses": [
        "Symbole de l’élément chimique « émanation », maintenant appelé radon (Rn)."
      ],
      "tags": [
        "obsolete"
      ],
      "topics": [
        "chemistry"
      ]
    },
    {
      "glosses": [
        "Symbole de l’élément chimique « émanium », maintenant appelé actinium (Ac)."
      ],
      "tags": [
        "obsolete"
      ],
      "topics": [
        "chemistry"
      ]
    },
    {
      "categories": [
        "Lexique en conventions internationales de la chimie"
      ],
      "glosses": [
        "Symbole chimique de l’éka-manganèse, élément prédit par Dmitri Mendeleïev en 1871  . En 1937, il est remplacé par le technétium (Tc)."
      ],
      "tags": [
        "obsolete"
      ],
      "topics": [
        "chemistry"
      ]
    }
  ],
  "synonyms": [
    {
      "sense": "Émanation (2) :",
      "word": "Rn"
    },
    {
      "sense": "Émanation (3) :",
      "word": "Ac"
    },
    {
      "sense": "Éka-manganèse (4) :",
      "word": "Tc"
    }
  ],
  "tags": [
    "invariable"
  ],
  "word": "Em"
}