"Cartesian square" meaning in English

{
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      "form": "Cartesian squares",
      "tags": [
        "plural"
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  "lang_code": "en",
  "pos": "noun",
  "senses": [
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          "langcode": "en",
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      "glosses": [
        "For a set X, the Cartesian product X² = X × X."
      ],
      "id": "en-Cartesian_square-en-noun-dRZzMMtz",
      "links": [
        [
          "set theory",
          "set theory"
        ],
        [
          "set",
          "set"
        ],
        [
          "Cartesian product",
          "Cartesian product"
        ]
      ],
      "raw_glosses": [
        "(set theory) For a set X, the Cartesian product X² = X × X."
      ],
      "topics": [
        "mathematics",
        "sciences",
        "set-theory"
      ]
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      ],
      "glosses": [
        "A pullback."
      ],
      "id": "en-Cartesian_square-en-noun-ZqcKXwfI",
      "links": [
        [
          "category theory",
          "category theory"
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          "pullback",
          "pullback"
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      "raw_glosses": [
        "(category theory) A pullback."
      ],
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        "category-theory",
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        "natural-sciences",
        "physical-sciences",
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  "word": "Cartesian square"
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  "forms": [
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      "form": "Cartesian squares",
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  "pos": "noun",
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        "For a set X, the Cartesian product X² = X × X."
      ],
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          "set",
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          "Cartesian product",
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      "raw_glosses": [
        "(set theory) For a set X, the Cartesian product X² = X × X."
      ],
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        "(category theory) A pullback."
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