Relation sumo#part__part_of (object,object)  this type should have been name sumo#part_of to respect the common reading conventions of parameters; all other mereological relations are defined in terms of this one; it means that the 1st argument is part of the 2nd; note that, since part is a reflexive_relation, every object is a part of itself
  exclusion:  contains
  supertype:  spatial_relation_from_entity_with_spatial_feature (pm)  part_of (pm)
  instance of:  partial_ordering_relation_type (pm)  spatial_relation_type (pm)
  subtype:  proper_part__proper_part_of (object,object)  the 1st argument is part of the 2nd but is not it; this is a transitive_relation and asymmetric_relation (hence an irreflexive_relation)
  subtype:  piece__piece_of__pieceof (substance,substance)  a specialized common sense notion of part for arbitrary parts of substances; quasi-synonyms are: chunk, hunk, bit, etc; compare component, another subrelation of part
  subtype:  component__component_of__componentof (corpuscular_object,corpuscular_object)  a specialized common sense notion of part for heterogeneous parts of complexes; the 1st argument is a component of the 2nd argument; examples: the doors and walls of a house, the states or provinces of a country, or the limbs and organs of an animal; compare with sumo#piece, another specialization of sumo#part
  subtype:  member (self_connected_object,collection)  a specialized common sense notion of part for uniform parts of collections; for example, each sheep in a flock of sheep would have the relationship of member to the flock