5b. Use Parentheses For Longer Searches

PubMed processes ANDs, ORs & NOTs in a left-to-right sequence.

Click Clear to clear the query box. You want to research remedies for the common cold. Type in: common cold AND vitamin C OR zinc. Click GO. These results are NOT on-target because PubMed retrieved all occurrences of "zinc" in the database. The hits containing zinc will not necessarily contain common cold.

Using parentheses would change the order in which PubMed processes the search statement. Example: common cold AND (vitamin C OR zinc).