Using AND and OR in Searches – OHIO University Libraries


George Boole

This page covers the technique of using connecting words to group sets of search terms so as to improve your search results.The words used to connect these sets of terms are called Boolean connectors (named after the 19th century British mathematician, George Boole).


To see how the Boolean connectors AND and OR work, try each of the searches linked below and compare the numbers of results you get from each one.

Use AND to reduce the number of items found:

global warming and sea level finds fewer items than either global warming by itself or sea levelby itself. Click on the links to compare the results of these 3 searches.

Use OR to combine synonymous or alternate terms and thus increase the number of items found:

global warming or climate change finds more items than either  global warming by itself or climate change by itself. Again, try these links and compare results.

With just your imagination and well-chosen search terms, you can create complex, but very powerful, searches, using both AND and OR in a single search. Note the use of parentheses to group the terms connected by OR:

(global warming or climate change) and sea level finds only those items that have either the term global warming or the term climate change as well as the term sea level.

(global warming or climate change) and (sea level or coastal flooding) finds those items that have at least one term from each group. Kind of a “mix and match” deal.