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Lund University


Biology library guide to information searches

Combine search words

Combine search words with search operators

To be able to build a proper search query you need to combine the search word correctly. To do this you should use search operators. Use CAPITALS when you write the search operators. Some databases accept lower case letters, but not all.


AND (boolean operator)

Example: bird AND migration

  • All search terms have to be included in the results
  • Limits the search results, i.e. fewer search results
  • Space between words means (most often) AND


OR (boolean operator)

Example: bird OR aves

  • At least one of the terms should be included in the results
  • Use for synonyms or other alternative terms
  • Widens the search, i.e. more search results


NOT (boolean operator)

Example: ecology NOT medicine

  • The term after NOT should not be included in the search results
  • Limits the search, i.e. fewer search results
  • Risk of missing some interesting results
  • Use when you get many irrelevant results, but sparingly!