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  "body": "\n## Summary\n\nThe term **elementary** was originally introduced by László Kalmár in the context of computability theory. He defined the class of **elementary recursive functions** (*\"Kalmár elementary functions\"*) as a subset of the primitive recursive functions — specifically, those that can be computed using a limited set of operations such as composition, bounded sums, and bounded products. These functions grow no faster than a fixed-height tower of exponentiation (for example, $O(2^{2^n})$). Not all primitive recursive functions are elementary; for example, tetration grows too rapidly to be included in the elementary class. The elementary recursive functions correspond to the class $\\mathcal{E}^3$ of the Grzegorczyk hierarchy.\n",
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