Boolean logic utilizes three primary operators: AND, OR,
and NOT. It is helpful to diagram the effects of these operators:
Using the word "AND" actually narrows the results obtained in
a search, while using the word "OR" broadens the results.
To see the difference, enter a custom search for acid rain on Lycos.
Try the search once with "OR" and then again with "AND" by
checking the appropriate boxes.
Which search gave you the most useful results?
Did you notice? Lycos defaults to search for ANY of the words you enter (Boolean "or"); most search engines assume you want ALL of the words (Boolean "and").
We can also limit the results by using the Boolean operator
Different search engines incorporate Boolean logic in different ways. It is important to read the instructions for each search engine before entering your search terms. See also the section Deciding Where to Search for more detail.
Proceed to Diagramming the Search.
Go back to Constructing the Search.