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  "body": "\n## Summary\n\nA quasi-analytic class is a class of [[smooth functions|0V33BNKZ9S]] in which a function is determined by its derivatives at a single point.\nReal [[analytic functions|081WKEDK6C]] form such a class, but there are larger ones.\nQuasi-analytic classes are defined by bounds on the growth of derivatives.\nThe [[Denjoy–Carleman theorem|KV0GW9K7JS]] says exactly which bounds give a quasi-analytic class.\n\n## Explanations\n\n### L1 human\n\nFor an analytic function, the derivatives at one point fix the function everywhere.\nFor general smooth functions this fails: a smooth function can vanish to all orders at a point and still be nonzero.\nQuasi-analytic functions keep the good property of analytic functions without being analytic.\nThey are smooth functions whose derivatives do not grow too fast.\n",
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