Boolean Operations

Boolean Operators

Boolean operators (pronounced “boo-lee-an”) are named after the mid-1800s mathematician George Boole and are advanced search methods designed to help you narrow your search. Boolean operators are logical terms used to combine keywords or define the relationships between keywords. For example: a search for spiral staircase would lead to the following results:

spiral

all documents with the word spiral in it and not necessarily having anything to do with staircases

staircase

all documents with the word staircase in it and not necessarily having anything to do with spiral staircases

Boolean operators allow words to be connected together to yield better or more accurate results for what you are really looking for. The most commonly used Boolean operators are listed below along with symbols that can be used in their place.

AND

+

NOT

-

OR

|

So, the search for spiral staircase could be refined if you typed spiral AND staircase; the search would then yield the correct results for documents that only talk about spiral staircases. Notice that the Boolean operator is in all capital letters. Some search engines require the Boolean operator to be in all caps and some do not. Because you may not know which search engines require all caps, it is a good idea to get into the habit of using all capital letters when you search with Boolean operators.

The examples that follow show you how to use Boolean operators:

Shakespeare AND clothing
Shakespeare + clothing

would yield the results of documents that talk about clothing in Shakespeare’s time or possibly costumes used in performances of Shakespeare’s plays

Shakespeare NOT clothing
Shakespeare - clothing

would yield the results of documents about Shakespeare’s time but would exclude results about clothing

Shakespeare OR clothing
Shakespeare | clothing

would yield the results of any document on the Internet about Shakespeare and any document about clothing; however, using these two operators would give you too many results. You would be better off searching for each keyword separately

Boolean operators can be combined to narrow searches even further, such as the following:

George Washington Carver AND inventions NOT peanut butter
(Yes, he invented peanut butter.)

This search would produce results that contain information about all of George Washington Carvers inventions except for peanut butter.

As you get more experienced in searching, you will notice that generally search engines find all variables when you use the singular version of words. For example, searching forocean will bring more choices than searching for oceans.

Some databases also include all variables automatically, but others require wildcards. A wildcard is a character that finishes part of a word. For example, the asterisk(*) added on to the end of the word ski tells the search engine to find all versions of that word. It would look for ski, skis, skiing, skied, skier, and skiers.