#tertium_quid__tertiumquid  some third thing similar to two opposites but distinct from both
  supertype:  #oppositeness__opposition  the relation between opposed entities
     supertype:  #relation  an abstraction belonging to or characteristic of two entities or parts together
        supertype:  pm#thing_that_can_be_seen_as_a_relation  usable as relation type
           supertype:  pm#thing_playing_some_role  category to classify things according to roles/viewpoints; classification under this category is application-dependant
              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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