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  "body": "\n## Definition\n\nA set is a collection of objects, called the elements of the set.\nFor an object $x$ and a set $A$, either $x$ is an [[element|0EZ758XE73]] of $A$, written $x \\in A$, or it is not, written $x \\notin A$.\nTwo sets $A$ and $B$ are equal when they have the same elements: for each $x$, $x \\in A$ if and only if $x \\in B$.\nA finite set can be written by a list of its elements in braces, for example $\\{1, 2, 3\\}$.\n\n## Remarks\n\nThe sets $\\{1, 2, 3\\}$, $\\{3, 2, 1\\}$ and $\\{1, 1, 2, 3\\}$ are the same set.\nIn [[Zermelo–Fraenkel set theory|0HE5WDQ9FJ]], \"set\" and \"$\\in$\" are primitive notions, and the axioms say how they behave.\nNot every collection can be a set. [[Russell's paradox|0HESMMSYEG]] shows this.\n\n## Explanations\n\n### L1 human\n\nA set is like a bag of objects, where only membership counts.\nThe bag $\\{1, 2, 3\\}$ contains $1$, $2$ and $3$, and nothing else.\nYou cannot put the same object in twice, and the objects have no order.\n",
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