Semantic Network

semantic network iconThe Semantic Network consists of (1) a set of broad subject categories, or Semantic Types, that provide a consistent categorization of all concepts represented in the UMLS Metathesaurus, and (2) a set of useful and important relationships, or Semantic Relations, that exist between Semantic Types. This section of the documentation provides an overview of the Semantic Network, and describes the files of the Semantic Network. Sample records illustrate structure and content of these files.

The UMLS Semantic Network is available in unit record and relational format and is distributed subject to these terms and conditions.

Semantic Groups

semantic group iconThe UMLS semantic network reduces the complexity of the Metathesaurus by grouping concepts according to the semantic types that have been assigned to them. For certain purposes, however, an even smaller and coarser-grained set of semantic type groupings may be desirable. The following principles were used to design the groupings: semantic validity, parsimony, completeness, exclusivity, naturalness, and utility. The semantic groups provide a partition of the UMLS Metathesaurus for 99.5% of the concepts.

Further information about the semantic groups can be found at:

The UMLS semantic groups are made available through a file called SemGroups.txt. There is one line in this file for each semantic type. The identifier and the name of the semantic group are repeated for each semantic type included in the group, before the identifier (TUI) and the name (STY) of the semantic type.


Email: NLM Support Center