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Cataloging and Metadata Management: Fundamentals of the NLM® Classification

Fundamentals of the NLM® Classification_index

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Structure of NLM Classification


  • Schedules are topical groupings of classification numbers
  • The NLM Classification includes schedules permanently excluded from Library of Congress Classification (LCC): QS-QZ; W-WZ
  • NLM class numbers are alphanumeric notations patterned after LCC
  • Unlike LCC, NLM class numbers are formatted with a space between the alpha and numerical call number. Exception: If the class number consists of a single letter and a single digit, it is entered without any space (e.g., W1, W2, W3, etc.)


   There are 36 schedules which denote broad subject categories:

  • Preclinical Sciences (QS-QZ)
  • General Health and Medicine (W-WB)
  • Diseases of the Whole Body; Aviation, Space, Naval Medicine (WC-WD)
  • Body Systems (WE-WL)
  • Specialty Areas (WM-WY)
  • History (WZ; 19th Century)

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