Boolean logic is a system that allows a searcher to set relationships between keywords or concepts when searching. The most commonly used Boolean commands are AND, OR, and NOT. Parentheses can be used to specify the relationship further. Using these operators can make your searches more precise and save time.
AND NARROWS:
Tells the database that you only want articles that contain ALL of the search terms
smoking AND nicotine
OR EXPANDS:
Tells the database that you want all articles that contain EITHER of the terms
smoking OR nicotine
NOT EXCLUDES:
Tells the database that you do not want any articles that contain a certain term
smoking NOT nicotine
JOINING NARROWS:
Tells the database that you want articles with EITHER of two terms AND another
(smoking OR nicotine) AND cancer
