"虚数単位" meaning in Japonais

{
  "categories": [
    {
      "kind": "other",
      "name": "Noms communs en japonais",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Japonais",
      "orig": "japonais",
      "parents": [],
      "source": "w"
    }
  ],
  "etymology_texts": [
    "Composé de 虚数, kyosū (« nombre imaginaire ») et de 単位, tan’i (« unité »)."
  ],
  "forms": [
    {
      "form": "きょすうたんい",
      "tags": [
        "hiragana"
      ]
    },
    {
      "form": "kyosū tan’i",
      "tags": [
        "transcription"
      ]
    }
  ],
  "lang": "Japonais",
  "lang_code": "ja",
  "pos": "noun",
  "pos_title": "Nom commun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Lexique en japonais des mathématiques",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Unité imaginaire."
      ],
      "id": "fr-虚数単位-ja-noun-I-HMb8mN",
      "topics": [
        "mathematics"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "\\kʲo.sɯː.taɴ.i\\"
    }
  ],
  "word": "虚数単位"
}

{
  "categories": [
    "Noms communs en japonais",
    "japonais"
  ],
  "etymology_texts": [
    "Composé de 虚数, kyosū (« nombre imaginaire ») et de 単位, tan’i (« unité »)."
  ],
  "forms": [
    {
      "form": "きょすうたんい",
      "tags": [
        "hiragana"
      ]
    },
    {
      "form": "kyosū tan’i",
      "tags": [
        "transcription"
      ]
    }
  ],
  "lang": "Japonais",
  "lang_code": "ja",
  "pos": "noun",
  "pos_title": "Nom commun",
  "senses": [
    {
      "categories": [
        "Lexique en japonais des mathématiques"
      ],
      "glosses": [
        "Unité imaginaire."
      ],
      "topics": [
        "mathematics"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "\\kʲo.sɯː.taɴ.i\\"
    }
  ],
  "word": "虚数単位"
}