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Information Literacy, Level Two

Boolean logic

When you were identifying your topic you chose some keywords.  One of the tabs in this tutorial describes subject headings.  Subject headings are only one part of the description of the item.  To search all parts of the record we use ANDs and ORs to connect keywords that an author or cataloger might  use when describing a book or journal.  Remember you may have to use synonyms, as different people use different words to describe the same thing.  When searching the catalog to find books, or databases to find articles, you need a special kind of logic called Boolean.  

Let's think about the topic friendship.  Simply typing in friendship gets you thousands of books and articles.  Even summarizing everything you found would be a very long paper.  So how do you narrow your topic?  Think of something you want to know about friendship.  


How does having friends affect your health, for example.  Most databases supply an AND if you do not specify how the words are to be connected.  An AND indicates that you want both keywords in the sentence to appear in the description of each book or article you find. Using AND will limit your search and retrieve less articles since it will only retrieve articles with the both keywords in it.

Friendship AND health

    will retrieve the book        


Families in society : boundaries and relationships

Chapter 8. Intersections of  health and well-being in women's lives and relationships at mid-life / 

Chapter 13. Boundaries of  friendship.


Both of the words you were looking for appeared in the description of the book found.


If you have several synonyms that mean the same thing, you connect the synonyms with OR.  The items retrieved can contain either word but do not have to contain both.

Friendship OR companionship will retrieve this book

"The friendship" ; "The gold Cadillac" by Mildred Taylor : teacher's guide.

health OR fitness will retrieve this book

Health and community design : the impact of the built environment on physical activity : Frank, Lawrence D. 

Note that the first book has nothing to do with health and the second has nothing to do with friendship.

We can use several Boolean operators in the same search.  It is good practice to use parentheses to group synonyms for the same concept.  This ensures that the database finds all the articles about each concept first, and then finds an item with one word for each of the concepts described.  The use of parentheses in searches is called nesting.

(friendship OR companionship) AND (health OR illness)

Video about boolean logic

Additional search techniques

Some additional hints about searching:

If your search produces articles about a topic that you don't want because one of your words has multiple meanings, you can use the word NOT.  For example, I am researching the topic of mythology and want to know about Taurus the bull.  Most of my results relate to my topic, but I am also getting articles about the Ford car named Taurus.

Search: taurus AND mythology NOT (car OR automobile)

Truncation is a way to search for all the words with the same root.  To find articles that mention child, children and childhood, search the following:

child* and education

The shift key and 8 key will create the *.

Nesting was mentioned above as a way of grouping synonyms.  Generally the database works from one side of a search statement to the other.  Consider this statement:

friendship AND siblings OR brother OR sisters

Since the database works from left to right, it would first find all the articles that contained both the word friendships and sibling [friendship AND siblings].  It would then add all the articles that contained the word brothers [OR brothers] and all the articles that contained the words sisters  [OR sisters].  The articles on brothers and sisters would not have to contain the word friendship.  Now let us consider this statement

Friendship AND (siblings or brothers or sisters)

The database is forced to find articles that contain either the word sibling or one of its synonyms (brothers or sisters). (siblings or brothers or sisters)   It then takes that group AND finds things within the group that also contain the word friendship.  Friendship and ().   Different databases process things differently.  Nesting lets you make sure that the terms are combined in the way that defines your topic.

Boolean activity

Use the links below to search the catalog.  Which Boolean operator (AND, OR) retrieves more results?  Can you explain why?  Choose that option and submit.  

Boolean activity
Search using AND: 101 votes (34.59%)
Search using OR: 191 votes (65.41%)
Total Votes: 292