Answered By: Mary Ann Cullen
Last Updated: Sep 12, 2016     Views: 79

Boolean operators are words used to connect search terms (keywords) to improve your results. Most search engines assume you want results containing all of the search terms you enter in the search box, but some research databases require that you use Boolean operators between terms. Even when not required, searching GALILEO, the GIL library catalogs or even search engines like Google can be more effective if you use Boolean operators appropriately.

The most commonly used Boolean operators are AND, OR, and NOT. 

AND - search results will contain both search terms

OR - search results will contain one or both search terms

NOT - search results will contain the first search term, but not if the term following NOT is included.

Here are some examples:

Boolean examples

To learn more about Boolean operators, try the Boolean Operator Tutorial from Colorado State University: