#building_block__unit  a single undivided natural entity occurring in the composition of something else; "units of nucleic acids"
  supertype:  physical_entity_part_or_substance (pm)
  subtype:  chemical_chain  couple.building_block  unit_cell  chemical_group  molecule
  part:  physical_part__part__piece  a portion of a natural object; "they analyzed the river into three parts"; "he needed a piece of granite"

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