OR is used to broaden your search. When you add OR between two or more search terms, your search results will include either of your search terms.
The blue area in the illustration to the right represents the results that would be returned for the search Cetacean OR Whale. All the articles will have both terms.
Lets take a closer look.
In the database, Web of Science, the searches for Cetacean, Whale, and Cetacean OR Whale break down like this:
Cetacean = 6,652 results
Whale = 19,749 results
Cetacean OR Whale = 22,935 results
Remember OR means mORe!
Follow Up Question: Why isn't the answer 26,401, the sum of Cetacean + Whale?
OR is especially helpful in these situations: