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BIOL 1500 Biology I

Boolean Operations

Once you determine your search terms (keywords), use Boolean operators (AND, OR, NOT) to combine or exclude search terms.

Using the keywords from the previous page (Heart Rate, Exercise), along with an additional keyword (Aerobics), we'll construct example searches using Boolean Operators with accompanying Venn Diagrams to help visualize what the search results will consist of.

Individual Venn Diagram circles for keywords Heart Rate, Exercise, Aerobics.

PubMed search tips:
- Enter Boolean operators in uppercase characters.
- PubMed processes searches in a left-to-right sequence. Use parentheses to "nest" concepts that should be processed as a unit and then incorporated into the overall search.

AND retrieves results that include all the search terms.

Venn Diagram for Heart Rate AND Exercise. Pubmed results equal 54599


OR retrieves results that include at least one of the search terms.

Venn Diagram for Heart Rate AND (Exercise OR Aerobics). Pubmed results 55747


Using parentheses to "nest" concepts to be processed as a unit can make a substantial difference in the search results. Move your mouse over the Venn Diagram below to compare using parentheses versus not using parentheses.


NOT excludes the retrieval of terms from your search.


Venn Diagram for Heart Rate AND (Exercise NOT Aerobics). Pubmed results 760