Do concept unique identifiers (CUIs) in UMLS have a hierarchy?

  • Yes. They do have a hierarchy. An is-a relationship exists. It is even a poly-hierarchy. Meaning that one concept can have multiple parent terms.
    – userJT
    Commented May 29, 2019 at 14:54

1 Answer 1


As far as I know, there is a hierarchy, but it is based on the original sources (ie not created by UMLS). For example, SNOMED concepts belong to a hierarchy. UMLS records this hierarchy in the mrhier table. It is probably best to consider the hierarchy based on the source's code, and not on the UMLS concept ID, as the mapping between UMLS CUIs and codes are often very rough. Source: https://www.ncbi.nlm.nih.gov/books/NBK9676/


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