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  "body": "\n## Summary\n\nA rack is a set with a [[binary operation|0M418FE7BB]] that distributes over itself and acts on the set by bijections.\nA quandle is a rack in which every element $a$ satisfies $a \\triangleleft a = a$.\nThe model example is conjugation in a group, $a \\triangleleft b = a b a^{-1}$, which keeps the properties of conjugation and forgets the group multiplication.\nThe three quandle axioms match the three Reidemeister moves of [[knot|QYEAZTYGPT]] diagrams, so each knot has a fundamental quandle, which is a strong [[knot invariant|GZQ5ZE3X6G]].\n\n## Explanations\n\n### L1 human\n\nIn a group, conjugating $b$ by $a$ moves $b$ to $a b a^{-1}$.\nA quandle keeps only this operation and its basic rules.\nKnot theory uses quandles by giving a label to each arc of a knot diagram.\nAt each crossing, the label of the arc that passes under changes by the operation with the label of the arc that passes over.\nThe rules of a quandle are exactly the rules that make this labelling unchanged by the usual moves of knot diagrams.\n",
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