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  "body": "\n## Definition\n\nLet $X$ be a set and let $k$ be a natural number.\nA $k$-combination of $X$ is a subset $S \\subseteq X$ with $|S| = k$.\n\nThe set of all $k$-combinations of $X$ is written $\\binom{X}{k}$.\n\n## Remarks\n\nA combination does not record an order of its elements. Two lists with the same elements in a different order give the same combination.\nFor $X = \\{a, b, c\\}$, the 2-combinations are $\\{a, b\\}$, $\\{a, c\\}$ and $\\{b, c\\}$.\nThe [[number of k-element subsets|0BFMR2FQ8B]] of an $n$-element set is the [[binomial coefficient|092GEF38YD]] $\\binom{n}{k}$.\n\n## Explanations\n\n### L1 human\n\nA combination is a selection of $k$ objects where the order does not matter.\nChoosing a team of 2 from Ann, Bob and Cy gives 3 teams, because the team $\\{$Ann, Bob$\\}$ is the same as $\\{$Bob, Ann$\\}$.\n",
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