#Hilbert_space  a metric space that is linear and complete and (usually) infinite-dimensional
  supertype:  #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"
        supertype:  #set  (mathematics) an abstract collection of numbers or symbols; "the set of prime numbers is infinite"
           supertype:  pm#collection  something gathering separated things (entities/situations)
              supertype:  pm#divisible_entity__divisibleentity  many classifications under this category are application-dependant
                 supertype:  pm#entity  something that can be "involved" in a situation
                    supertype:  pm#thing__something___T__t___3D_or_4D_thing_or_anything_else  any category (type or individual) is instance of this type; any type is also a subtype of this type
                 supertype:  pm#divisible_thing__divisiblething
                    supertype:  pm#thing__something___T__t___3D_or_4D_thing_or_anything_else  any category (type or individual) is instance of this type; any type is also a subtype of this type

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