The UMLS includes the Metathesaurus, the Semantic Network, and the SPECIALIST Lexicon and Lexical Tools. The Metathesaurus is the biggest component of the UMLS. It is a large biomedical thesaurus that is organized by concept, or meaning, and it links similar names for the same concept from nearly 200 different vocabularies. The Metathesaurus also identifies useful relationships between concepts and preserves the meanings, concept names, and relationships from each vocabulary.
You can access the Metathesaurus via download, browser, or API.
Need an account? Sign up on the UMLS Terminology Services (UTS) Web site.
Release Information
See Appendix 1 of the UMLS Metathesaurus License Agreement for a list of all vocabularies included in the latest version.
Follow these links for details about the release:
- Current Release Documentation -- Release notes, bugs, license copy, metadata, and general statisics for the current Metathesaurus release.
- Vocabulary Documentation -- Synopsis, contact information and statistics for each new and updated vocabulary in the current Metathesaurus release.
- Release Documentation Archive -- Documentation dating from 2002AA.
Education
Read more about the Metathesaurus and its data files in UMLS Reference Manual. Relevant chapters include:
- Metathesaurus -- overview of the Metathesaurus and its organizational structure.
- Rich Release Format (RRF) Data Files -- Descriptions of each file (MRCONSO.RRF, MRREL.RRF, etc.) including column names and samples records from each file
- Original Release Format (ORF) Data Files -- Descriptions of each file (MRCON, MRREL, etc.) including column names and samples records from each file
More Information
- MetamorphoSys -- UMLS installation wizard and Metathesaurus customization tool included in each UMLS release.
- UMLS Database Query Diagrams -- Query diagrams that present use cases and how the data files can be joined (or queried) to find all relevant data for the use cases.
- Vocabulary FAQ -- Frequently Asked Questions about the sources vocabularies in the Metathesaurus.
- Vocabulary Mappings -- Current NLM mapping efforts.
Last Reviewed: April 12, 2016