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  "body": "\n## Summary\n\nA standard Borel space is a measurable space whose measurable sets are the Borel sets of some Polish topology.\nThese are the measurable spaces met in practice, such as the real line, $[0, 1]$ and spaces of sequences.\nBy a theorem of Kuratowski, two standard Borel spaces are isomorphic exactly when they have the same cardinality.\n\n## Explanations\n\n### L1 human\n\nMany different-looking spaces carry the same measurable structure.\nThe real line, the unit interval and the plane look different as topological spaces, but as measurable spaces with their Borel sets they are all the same.\nA standard Borel space is a measurable space that comes from a nice topological space in this way.\nUp to isomorphism there are only few of them: the finite ones, the countably infinite one and the one of the real line.\n",
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