#pigeonholing__grouping  a system for classifying things into groups
  supertype:  classification_system  a system for classifying things
  subtype:  ABO_blood_group_system__ABO_system__ABO_group  a classification system for the antigens of human blood; used in blood transfusion therapy; four groups are A and B and AB and O

No statement uses or specializes pigeonholing; click here to add one.