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  "body": "\n## Summary\n\nMorrey spaces and Campanato spaces measure the size of a function on small balls, uniformly over all centres.\nA Morrey space asks that the $L^p$ mass of $f$ on a ball of radius $r$ is at most a constant times $r^\\lambda$.\nA Campanato space asks the same of the oscillation of $f$ around its mean on the ball.\nSpecial cases are [[Lebesgue spaces|SASP14MA1Z]], [[bounded mean oscillation|QJYTXFT8Y4]] and [[Hölder continuous|012PBA0FMD]] functions.\nThey are a basic tool for the regularity of solutions of elliptic equations.\n\n## Explanations\n\n### L1 human\n\nTake a function and look at it through a small round window of radius $r$.\nMeasure how much of the function you see, or how much it varies, inside the window.\nIf this amount shrinks like a power $r^\\lambda$ as the window gets smaller, wherever you put it, the function lies in the Morrey or Campanato space with exponent $\\lambda$.\nA larger $\\lambda$ means a tamer function.\nFor instance, a function with a mild spike such as $\\abs{x}^{-a}$ is still allowed for small enough $\\lambda$.\n",
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  "name": "Morrey–Campanato space",
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