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Unified Medical Language System® (UMLS®)


The SPECIALIST Lexicon is an English lexicon (dictionary) that includes biomedical terms as well as commonly occurring English words. The lexical entry for each word or term records the following information:

  • Syntactic (syntax information)
  • Morphological (inflection, derivation, and composition information)
  • Orthographic (spelling information)

Currently the SPECIALIST Lexicon contains over 200,000 terms and is used by the lexical tools to aid in Natural Language Processing. Words are selected for entry into the Specialist lexicon from a variety of sources:

  • The UMLS Test Collection of MEDLINE abstracts
  • Dorland's Illustrated Medical Dictionary
  • The American Heritage Word Frequency Book
  • Longman's Dictionary of Contemporary English
  • Current MEDLINE citation records

Last Reviewed: July 29, 2016