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Unified Medical Language System® (UMLS®)

Semantic Relationships

Of the fifty-four semantic relationships the primary link between most semantic types is the isa relationship. The 'isa' relationship establishes the hierarchy of types within the Semantic Network and is used for deciding on the most specific semantic type available for assignment to a Metathesaurus concept.

Some examples of the 'isa' relationship:

  • Animal isa Entity
  • Carbohydrate isa Chemical
  • Human isa Mammal

There are five major, non-hierarchical relationships:

  • Physically related to
  • Spatially related to
  • Temporally related to
  • Functionally related to
  • Conceptually related to

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