This is an abbreviation for polyhierarchical classification.

polyhierarchical classification

A hierarchy in which each node has one or more parents.


  • The  subtype relationships of SNOMED CT create a polyhierarchical classification.
  • A polyhierarchical classification can be represented as a graph in which each node has a one or more directed links to or from other nodes.
  • A node in a polyhierarchical classification cannot be a  descendant of itself, which means the hierarchy must not contain cyclic  relationships. This type of hierarchy is therefore known as a  directed acyclic graph


  • The diagram below shows a polyhierarchy. Each node has one or more parent node so there can be multiple paths from a node to the top (or root) of the hierarchy. 
    For example from node V the paths include the following:
    • V→N→F→B→A
    • V→N→F→C→A
    • V→G→C→A 

Figure 1: Hierarchy Illustration - Polyhierarchical Classification


  • Polyhierarchy

Related Links

  • No labels