"3rd grader" meaning in English

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      "expansion": "3rd grade + -er",
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  "etymology_text": "From 3rd grade + -er.",
  "forms": [
    {
      "form": "3rd graders",
      "tags": [
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  "lang_code": "en",
  "pos": "noun",
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          "word": "third grader"
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        {
          "kind": "topical",
          "langcode": "en",
          "name": "Education",
          "orig": "en:Education",
          "parents": [
            "Society",
            "All topics",
            "Fundamental"
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      ],
      "glosses": [
        "Alternative spelling of third grader"
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      "id": "en-3rd_grader-en-noun-o-ZIi06h",
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  ],
  "word": "3rd grader"
}

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        "2": "3rd grade",
        "3": "er",
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  ],
  "etymology_text": "From 3rd grade + -er.",
  "forms": [
    {
      "form": "3rd graders",
      "tags": [
        "plural"
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    }
  ],
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  "lang_code": "en",
  "pos": "noun",
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          "word": "third grader"
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  "word": "3rd grader"
}