Distance Education Resources: Library Tools

Many library databases and Web search engines support Boolean searches.  Boolean searching is based on combinations of keywords that are connected by operators.  There are three basic operators: AND, OR, and NOT. These operators are used to limit, widen or define the search strategy.

The Boolean operator AND retrieves every document that contains both of the words specified. Combining search terms with AND in a search narrows the search results, thus retrieving more specific results. To locate information on bell related to chime topics use the search terms:  

bell AND chime

Search processes retrieve every record containing both words belland chime.  More combinations may be added to narrow the search, such as bell AND chime AND tone.

The Boolean operator OR broadens a search to include documents which have either keyword.  OR is also used when there are common synonyms for a concept or variant spelling of a word.  To find information on heart attack use:

heart attack OR stroke

All documents containing either term heart attack or stroke, or both terms heart attack and stroke will be retrieved, which may result in a large numbers of documents.

The Boolean operator NOT narrows a search by excluding unwanted terms. NOT eliminates records or documents containing the second search term. To find information on life but not support use:

 life NOT support

The search results in documents with the keyword life and excludes the term support.