"couldn't" meaning in 英語

{
  "categories": [
    {
      "kind": "other",
      "name": "英語",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "英語 縮約形",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "英語",
  "lang_code": "en",
  "pos": "contraction",
  "pos_title": "縮約形",
  "senses": [
    {
      "examples": [
        {
          "text": "Couldn't be better. - これ以上ないほどよい。最高だ。"
        }
      ],
      "glosses": [
        "could not"
      ],
      "id": "ja-couldn't-en-contraction-fq8SYGOD"
    }
  ],
  "word": "couldn't"
}

{
  "categories": [
    "英語",
    "英語 縮約形"
  ],
  "lang": "英語",
  "lang_code": "en",
  "pos": "contraction",
  "pos_title": "縮約形",
  "senses": [
    {
      "examples": [
        {
          "text": "Couldn't be better. - これ以上ないほどよい。最高だ。"
        }
      ],
      "glosses": [
        "could not"
      ]
    }
  ],
  "word": "couldn't"
}