#metric_space  a set of points such that for every pair of points there is a nonnegative real number called their distance that is symmetric and satisfies the triangle inequality
  supertype:  topological_space__topologicalspace__space  (mathematics) any set of points that satisfy a set of postulates of some kind; "assume the vector space is finite dimensional"
  subtype:  Euclidean_space  a space in which Euclid's axioms and definitions apply; a metric space that is linear and finite-dimensional
  subtype:  Hilbert_space  a metric space that is linear and complete and (usually) infinite-dimensional

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