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Developing a Research Topic: Boolean, Truncation, and Wildcards

Boolean Operators

Boolean Operators


  • Allow a database search to be narrowed, broadened or made more precise.
  • There are three Boolean operators:  AND, OR, and NOT.
  • AND, OR, NOT are inserted between each search term.




  • Used for narrowing or focusing a search topic. 
  • Specifies that both search terms must be present in the results. 


Example: Teenagers AND Violence

Two articles merging into one to demonstrate Boolean Operator And. You can search for articles on each aspect of your overall topic like teenagers or violence. But you can combine into one search by using AND. Teenagers AND Violence. The search results grow smaller as you use AND.



  • Used for expanding or broadening a search topic
  • Specifies that either search term can be present in the results. 
  • Often used to include synonyms or related terms.

Example: Teenager OR Juvenile OR Adolescent

Search results merging to demonstrate Boolean Operator Or. You can search with words that are synonyms (juvenile, teenager, adolescent) individually or by combining them by place OR between each word.  Juvenile OR Teenager OR Adolescent. Search results grower lower as you use OR.



  • Used to eliminate false hits, or get rid of that one term that you don't want in your results list. 
  • Specifies that the first term but not the second can be present in the results. 

Example: Teenagers NOT Violence. 



Nesting, Truncation and Wildcards

Nesting or Parentheses


  • An alternative to a database's Advanced Search
  • Allows you to construct complex searches combining AND, OR, NOT by grouping search terms appropriately



 (Teenagers OR Juveniles) AND Violence




  • Expands the search to locate all words beginning with the same root 
  • Symbol to truncate is usually an asterisk (*)
    • Example: teenwill return teen, teens, teenage, teenager, etc.
  • Useful to include any variants authors might use to describe their research
  • Not all words can effectively be truncated
    • Example: Trying to truncate woman as wom* will return wombat, womb, as well as woman and women. 




  • Used in the middle of a word to match usually known variants of a term.
  • A wildcard usually represents a single character
  • Symbol to represent the single character is usually a question mark (?) but this can vary by database. 
    • Example: wom?n will return woman, women, and womyn.


Note: These search tools involve using various symbols.  The symbols change depending on the database's vendor/interface you're dealing with, and the symbols may change over time within one of these vendors/interfaces.  If you have any questions about what symbols are used in a database, check its "Help" section.


Do you have any further questions about Boolean Operators and other database tips and tricks?  Chat with a Reference Librarian!