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Library Research E-Textbook - Instructor Version: Boolean Operators and Truncation

Introduction to Boolean Operators

From Bobish & Jacobson's The Information Literacy User's Guide (pgs. 21-24)

One way to limit a database search is to use Boolean operators; words you can add to a search to narrow or broaden your search results. They are and, or, and not. You can usually find these words in the advanced search query area of a database.

Database searching can seem confusing at first, but the more you use databases, the easier it gets.  And most of the time, the results you are able to retrieve are superior to the results that you will get from a simple Internet search.


And will narrow your search. For example, if you are interested in fresh water fishing, you would enter the terms "fish and freshwater." Your results would then include records that only contained both of these words.

The green overlapping area in the diagram above represents the results from the "fish and freshwater" search.


Or will broaden your search and is usually used with synonyms. If you are interested in finding information on mammals found in the Atlantic Ocean, you could enter the terms "whales or dolphins."

The circles above represent the or search. All of the records will contain one or the other, or both of your search terms will be in your results list.


Not will eliminate a term from your results. If you were looking for information on all Atlantic Ocean fish except Bluefish, you would enter "fish not bluefish."

The larger green circle represents the results that you would receive with this search.


From Bobish & Jacobson's The Information Literacy User's Guide (pgs. 39)

Because computers are very literal, they usually look for the exact terms you enter.  The perfect article may use the plural form of a word you need, rather than the singular; therefore, it is helpful to understand how to use trunciation in your searches.  Trunciation, or searching on the root of the word and whatever follows, accomplishes just this.

If you search on

Entrepreneur* and (adolescents or teens)

You will get items that refer either to the singular or the plural version of the word entrepreneur, but also entrepreneurship.

Look at these examples:



Think of two or three words you might retrieve when searching on these roots.


Click here to proceed to the next page of the module, Lateral Searching.

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