PubMed Tutorial from The Levy Library: Truncation
Using Truncation (Sparingly)
Truncation is a way to search for variant endings of a text string or word stem. Truncation is represented by the asterisk (*), sometimes referred to as a "wildcard". It can be used to search for all terms that begin with that basic word root. For example, a search for smok* finds citations with the words smoke, smoked, smoker, smoking, smokestoppers and over 100 more words and phrases. When considering using an asterisk, bear in mind that doing so may bring in terms that have nothing to do with your search. For example, a search for residen* that the searcher hopes will bring up citations on residents and residency will also include residence, residential, and other terms with no bearing on residents and residency.
Try this: Clear your earlier search and search for hospital*
Check the Search details box. You will see your search will return results for terms such as hospital, hospitals, hospitalist, hospitalists and hospitalization. Using the wildcard will also include several foreign language variations in your search (e.g. hospitalista, hospitalgesellschaft, hospitalisation).
Although truncation helps you find word variants, it turns off Automatic Term Mapping. When you truncate a search term, MeSH and synonyms are not added to your search.
Note that PubMed restricts retrieval to the first 600 variations of the truncated term. When this occurs, PubMed will display a warning message.
Be aware that if you use truncation for one concept in your search, you must use an AND to combine it with other concepts (whereas without truncation the AND is implied in the absence of another boolean operator [OR, NOT]).