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  "body": "\n## Definition\n\nA cardinal number is the [[cardinality|0JTGRV4WT4]] $|A|$ of some set $A$.\nIn ZFC, the von Neumann definition takes $|A|$ to be the least [[ordinal|0RDJK7EQYY]] $\\kappa$ such that $\\kappa$ is [[equinumerous|08EJHHMB5R]] with $A$. A cardinal number is then an ordinal that is not equinumerous with any smaller ordinal.\n\n## Remarks\n\nThe finite cardinals are the natural numbers $0, 1, 2, \\dots$.\nThe least infinite cardinal is [[aleph-null|0V2H5PGJ9B]], the cardinality of $\\mathbb{N}$.\nCardinals have an order, an addition, a multiplication and an exponentiation.\nThe sum $|A| + |B|$ is the cardinality of a disjoint union, and $|A| \\cdot |B| = |A \\times B|$.\nThe power $|B|^{|A|}$ is the cardinality of the set of functions from $A$ to $B$.\n\n## Explanations\n\n### L1 human\n\nA cardinal number answers \"how many?\".\nFor finite sets, the answers are $0, 1, 2, \\dots$.\nFor infinite sets, there are many different answers, such as $\\aleph_0$ for $\\mathbb{N}$ and $\\mathfrak{c}$ for $\\mathbb{R}$.\n",
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