"facultative" meaning in Anglais

{
  "categories": [
    {
      "kind": "other",
      "name": "Adjectifs en anglais",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Lemmes en anglais",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Wiktionnaire:Étymologies manquantes en anglais",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Anglais",
      "orig": "anglais",
      "parents": [],
      "source": "w"
    }
  ],
  "etymology_texts": [
    "Étymologie manquante ou incomplète. Si vous la connaissez, vous pouvez l’ajouter en cliquant ici."
  ],
  "lang": "Anglais",
  "lang_code": "en",
  "pos": "adj",
  "pos_title": "Adjectif",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Termes soutenus en anglais",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Facultatif."
      ],
      "id": "fr-facultative-en-adj-obbUzezw",
      "tags": [
        "formal"
      ]
    },
    {
      "categories": [
        {
          "kind": "other",
          "name": "Termes soutenus en anglais",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Relatif à la faculté mentale."
      ],
      "id": "fr-facultative-en-adj-HT46ccnH",
      "tags": [
        "formal"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "\\ˈfæk.əl.ˌteɪ.tɪv\\"
    }
  ],
  "synonyms": [
    {
      "word": "optional"
    }
  ],
  "word": "facultative"
}

{
  "categories": [
    "Adjectifs en anglais",
    "Lemmes en anglais",
    "Wiktionnaire:Étymologies manquantes en anglais",
    "anglais"
  ],
  "etymology_texts": [
    "Étymologie manquante ou incomplète. Si vous la connaissez, vous pouvez l’ajouter en cliquant ici."
  ],
  "lang": "Anglais",
  "lang_code": "en",
  "pos": "adj",
  "pos_title": "Adjectif",
  "senses": [
    {
      "categories": [
        "Termes soutenus en anglais"
      ],
      "glosses": [
        "Facultatif."
      ],
      "tags": [
        "formal"
      ]
    },
    {
      "categories": [
        "Termes soutenus en anglais"
      ],
      "glosses": [
        "Relatif à la faculté mentale."
      ],
      "tags": [
        "formal"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "\\ˈfæk.əl.ˌteɪ.tɪv\\"
    }
  ],
  "synonyms": [
    {
      "word": "optional"
    }
  ],
  "word": "facultative"
}