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  "body": "\n## Definition\n\nA [[set|0SJ3RX9TXA]] $A$ is finite when there is a natural number $n$ such that $A$ is [[equinumerous|08EJHHMB5R]] with $\\{1, 2, \\dots, n\\}$.\nFor $n = 0$, this set is the [[empty set|0ECVK59Y03]].\nThe number $n$ is unique, and it is the number of elements of $A$.\n\n## Remarks\n\nSubsets, finite unions, finite products and the power set of finite sets are finite.\nA finite set is not equinumerous with any proper subset of itself. This is the pigeonhole principle.\nA set that is not finite is [[infinite|01MKW4R283]].\n\n## Explanations\n\n### L1 human\n\nA set is finite when you can count its elements and stop.\nThe set of planets of the Solar System is finite, and so is the set of primes less than $100$.\n",
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