"critical function" meaning in English

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      "expansion": "critical function (plural critical functions)",
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  "lang_code": "en",
  "pos": "noun",
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      "glosses": [
        "Any function, in the calculus of variations, that satisfies the Euler equations"
      ],
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          "mathematics",
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          "calculus of variations",
          "calculus of variations"
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          "Euler equation",
          "Euler equation"
        ]
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      "raw_glosses": [
        "(mathematics) Any function, in the calculus of variations, that satisfies the Euler equations"
      ],
      "topics": [
        "mathematics",
        "sciences"
      ]
    }
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  "word": "critical function"
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        "Any function, in the calculus of variations, that satisfies the Euler equations"
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          "mathematics",
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        "(mathematics) Any function, in the calculus of variations, that satisfies the Euler equations"
      ],
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        "mathematics",
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  "word": "critical function"
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