1999 UMLS Metathesaurus

• 626,313 concepts (Oculus, eye =1)

• 1,134,413 “terms” (Eye, Eyes, eye = 1)

• 1,358,891 “strings”/concept names

  • (Eye, Eyes, eye = 3)

• ~50 source vocabularies

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The UMLS Metathesaurus is one of the largest scale vocabularies I know of.

Strings of characters representing names of things come from 50 different source vocabularies. They are aggregated into “terms”, which name a concept and all normalize to the same string. Multiple terms can be aggregated together as naming the same concept.

Thus, Oculus and eye name the same concept.

Eye, Eyes, and eye all normalize to the same string, and can be thought of as the same term.

However, they are all different strings. Not identical because of case, plural