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  "body": "\n## Summary\n\nA perfect set in a [[topological space|0CQHFPGJ45]] is a [[closed set|0ZCK8DQYN1]] without [[isolated points|0A1YXSKB48]].\nEquivalently, it equals its own [[derived set|8ZAPAPYJFG]].\nIn the real line, every nonempty perfect set is uncountable, and the [[Cantor set|0BXNDZFQME]] is the standard example.\n\n## Explanations\n\n### L1 human\n\nA perfect set contains all the points it accumulates at, and none of its points stands alone.\nEvery point of it has other points of the set crowding around it.\nThe closed interval $[0, 1]$ is perfect.\nThe Cantor set, obtained by removing middle thirds again and again, is perfect too, although it contains no interval at all.\n",
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