"必要悪" meaning in Japanese

{
  "forms": [
    {
      "form": "必要悪",
      "ruby": [
        [
          "必",
          "ひつ"
        ],
        [
          "要",
          "よう"
        ],
        [
          "悪",
          "あく"
        ]
      ],
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "hitsuyō aku",
      "tags": [
        "romanization"
      ]
    },
    {
      "form": "fitueuaku",
      "tags": [
        "romanization"
      ]
    },
    {
      "form": "ひつえうあく",
      "roman": "fitueuaku",
      "tags": [
        "hiragana",
        "historical"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ひつよう あく",
        "head": "必要悪",
        "hhira": "ひつえうあく"
      },
      "expansion": "必(ひつ)要(よう)悪(あく) • (hitsuyō aku) ^(←ひつえうあく (fitueuaku)?)",
      "name": "ja-noun"
    }
  ],
  "lang": "Japanese",
  "lang_code": "ja",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Japanese entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese links with redundant alt parameters",
          "parents": [
            "Links with redundant alt parameters",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese links with redundant wikilinks",
          "parents": [
            "Links with redundant wikilinks",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese terms with 3 kanji",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese terms with redundant sortkeys",
          "parents": [
            "Terms with redundant sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "necessary evil"
      ],
      "id": "en-必要悪-ja-noun-Ql1hfDWL",
      "links": [
        [
          "necessary evil",
          "necessary evil"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[çit͡sɨjo̞ː a̠kɯ̟]"
    }
  ],
  "word": "必要悪"
}

{
  "forms": [
    {
      "form": "必要悪",
      "ruby": [
        [
          "必",
          "ひつ"
        ],
        [
          "要",
          "よう"
        ],
        [
          "悪",
          "あく"
        ]
      ],
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "hitsuyō aku",
      "tags": [
        "romanization"
      ]
    },
    {
      "form": "fitueuaku",
      "tags": [
        "romanization"
      ]
    },
    {
      "form": "ひつえうあく",
      "roman": "fitueuaku",
      "tags": [
        "hiragana",
        "historical"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ひつよう あく",
        "head": "必要悪",
        "hhira": "ひつえうあく"
      },
      "expansion": "必(ひつ)要(よう)悪(あく) • (hitsuyō aku) ^(←ひつえうあく (fitueuaku)?)",
      "name": "ja-noun"
    }
  ],
  "lang": "Japanese",
  "lang_code": "ja",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Japanese entries with incorrect language header",
        "Japanese lemmas",
        "Japanese links with redundant alt parameters",
        "Japanese links with redundant wikilinks",
        "Japanese nouns",
        "Japanese terms spelled with fourth grade kanji",
        "Japanese terms spelled with third grade kanji",
        "Japanese terms with 3 kanji",
        "Japanese terms with IPA pronunciation",
        "Japanese terms with IPA pronunciation missing pitch accent",
        "Japanese terms with redundant sortkeys",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "necessary evil"
      ],
      "links": [
        [
          "necessary evil",
          "necessary evil"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[çit͡sɨjo̞ː a̠kɯ̟]"
    }
  ],
  "word": "必要悪"
}

{
  "called_from": "parser/304",
  "msg": "HTML tag <span> not properly closed",
  "path": [
    "必要悪"
  ],
  "section": "Japanese",
  "subsection": "noun",
  "title": "必要悪",
  "trace": "started on line 2, detected on line 2"
}

{
  "called_from": "parser/1336",
  "msg": "no corresponding start tag found for </span>",
  "path": [
    "必要悪"
  ],
  "section": "Japanese",
  "subsection": "noun",
  "title": "必要悪",
  "trace": ""
}