Module 3—Selecting the Main Concept: Identifying Subject Headings as Primary or Secondary

Identifying Subject Headings as Primary or Secondary

• Optionally, libraries may choose to follow NLM practice and identify terms as either primary or secondary headings

• The primary heading(s) represent the main topic of the item being cataloged and will lead the cataloger to and correspond with the classification number to be assigned

• Prefer one primary subject per item, unless the main topic cannot be adequately covered by one primary heading (or heading/subheading combination)
       Example:
  • A work on fire prevention in hospitals would require the coordination of the MeSH terms Hospitals and Fires (with the subheading prevention & control) to get to the appropriate classification number of WX 185. Therefore both of these headings would be treated as primary. (Cf. Fundamentals of the NLM Classification, Module 4—General Principles)

• All other subjects are identified as secondary subject headings
       Example:
  • A work on acupuncture for chronic low back pain would have the primary subject Low Back Pain (with the subheading therapy) and secondary subjects for Acupuncture Therapy and Chronic Disease, since NLM prefers to classify by disease, regardless of special emphasis on diet, drug, therapy or diagnostic procedure