This may retrieve articles which had nothing to do with the extinction of dinosaurs, however. This will retrieve articles containing either term. There may not be any good synonyms for some concepts, such as extinction. Truncation Another useful trick for broadening your search is to truncate a stem word. Be careful where you truncate, however.
Most databases also have some form of controlled vocabulary.
Finding out which term the index uses can increase the number of articles you find. The subject lists for the indexes at the Biology Library are kept near the computers. These may help you. Other online helps include a listing of the words or phrases used by the system. If you need more help, the manuals for the computer indexes are kept near the stations along with other helpful material.