Most library catalogues, databases and search engines use standard boolean operators to combine search terms.

There are three common boolean operators: AND, OR and NOT.

The not operator allows search words to be excluded from a search.

For example: (beverages not alcoholic) excludes any record containing the second term.

And and or are most commonly used when searching; not is used most rarely. Use not with caution as you may inadvertently exclude useful material.

Let's now look at and and or in more detail.

Note: Check the Help screens of the search tool to determine what operators are valid.