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United States National Library of Medicine National Institutes of Health

Introduction to Boolean Logic (continued)

NOT:

  • Retrieves a set from which citations to articles containing specified search terms following the NOT operator are eliminated.

Example: arthritis NOT letter arthritis NOT letter

Note in the diagram to the right and in the sample search results below that the retrieval is a portion of the total retrieval for arthritis – that portion not including the term letter.

Search terms

Results

arthritis

167,933

letter

617,646

arthritis NOT letter

159,681

  • Use the NOT operator with caution; you might eliminate relevant articles.

 

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Last reviewed: 28 April 2009
Last updated: 10 October 2008
First published: 20 March 2001
Metadata| Permanence level: Permanent: Dynamic Content