Skip to Main Content

Find it! How to find resources at the library: How to Read Call Numbers

How to find all the library things

NLM Classification

The Library uses the NLM classification system for cataloging our books. A few helpful tips for when you are reading a call number:

  • All letters are kept in alphabetical order and alphabetized as if they were a word.
  • Nothing comes before something. Ex: A1 comes before AA1, C45 comes before C45a.
  • Read each line as follows:
    • First line is read as if it were a word.
    • Second line is read as a whole number.
    • Third line begins with letters that are read as if they were a word, followed by numbers that are read as a decimal point, reading the numbers place by place. Ex.: C745 comes before C8. Letters that follow numbers are read as if they were a word.
    • There may be a fourth line comprised of letters and numbers. Follow the same rules as the third line.
    • Subsequent line is the year of publication.
    • Subsequent line may list volume numbers.


Preclinical Sciences:

  • QS Human Anatomy
  • QT Physiology
  • QU Biochemistry. Cell Biology and Genetics
  • QV Pharmacology
  • QW Microbiology and Immunology
  • QX Parasitology
  • QY Clinical Pathology
  • QZ Pathology

Medicine and Related Subjects:

  • W General Medicine. Health Professions
  • WA Public Health
  • WB Practice of Medicine
  • WC Communicable Diseases
  • WD Disorders of Systemic, Metabolic, or Environmental Origin, etc.
  • WE Musculoskeletal System
  • WF Respiratory System
  • WG Cardiovascular System
  • WH Hemic and Lymphatic Systems
  • WI Digestive System
  • WJ Urogenital System
  • WK Endocrine System
  • WL Nervous System
  • WM Psychiatry
  • WN Radiology. Diagnostic Imaging
  • WO Surgery
  • WP Gynecology
  • WQ Obstetrics
  • WR Dermatology
  • WS Pediatrics
  • WT Geriatrics. Chronic Disease
  • WU Dentistry. Oral Surgery
  • WV Otolaryngology
  • WW Ophthalmology
  • WX Hospitals and Other Health Facilities
  • WY Nursing
  • WZ History of Medicine. Medical Miscellany
  • 19th Century Schedule

Need an overview of the classification so you can browse for a specific content area? Take a look at the NLM Classification Poster: