AND, OR, NOT
(Boolean Operators)

Using the Boolean operators (AND, OR, NOT) to combine keywords in a database search allows you to narrow or expand your search. To build a complex search using two or more Boolean operators, you will need to learn the advanced technique of nesting.

In the Venn diagrams below, the area retrieved is the yellow (or most lightly shaded) area. 

• Use AND to narrow a search. BOTH terms must be present in any references you retrieve.

Example: global warming AND forests

• Use OR to expand a search. Your search will retrieve records with EITHER of the terms.

 

Example: ethanol OR methanol

OR is most often used to combine synonyms or like terms.

• Use NOT to exclude a term. Records with the first term will be retrieved, but any records with the second term will be eliminated.

Example: california NOT baja