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HEMT 139: Global Adventures

Introduction to Boolean Operators

Boolean Operators are words that connect keywords (search terms) together to broaden or narrow the results retrieved. In library research they are often used with the library's research databases or the library catalog. 

The three Boolean operators are AND, OR, and NOT.

  • AND narrows your search results by limiting your results to those that contain both words connected with AND.
  • OR expands your search results by including results that contain one word, the other word, or both words.
  • NOT narrows your search results by limiting your results to those that contain the word you designate before NOT, but not the word after NOT.

One way to visualize Boolean Operators is to use a Venn diagram. See below or watch the video to the right.

Boolean Operator Venn Diagram indcating how a search of Peanut Butter and Jelly changes your results based on the boolean operator used to combine them. AND shades only the middle of the diagram, indicating any results would only have peanut butter and jelly in them. OR indicates that every result with peanut butter, with jelly, and with peanut butter and jelly would appear. Searching for Peanut Butter NOT Jelly indicates that only peanut butter would appear.

Boolean Operators

Different databases may have different rules on how you use boolean operators. For example, the library's Discovery Search requires that they be entered in all capital letters. So your search results for "College students" OR "University students" could be different from your results for "College students" or "University students".

Boolean Operators in Discovery Search

The screenshots below demonstrate how Boolean Operators can affect a search's results using the library's Discovery Search as an example. Many of the library's electronic databases also have help features that explain how users may utilize Boolean Operators in your searches.