Truncation is represented by the asterisk (*), sometimes referred to as a "wildcard."
Example: pharm* retrieves documents with the word pharmacology, as well as the pharmacy, pharmaceutical, etc.
Important Note: Automatic term mapping already accounts for some alternate endings in its algorithm. Using truncation turns off automatic term mapping enturely.
When the (*) asterisk is placed within a word, it serves as a wildcard to search for multiple spellings of a word.
Example: sul*ur retrieves sulphur and sulfur
PubMed processes search queries from left to right. To specify precedence, enclose terms and operators in parentheses within your search statement. You can nest and combine a search statement with the following Boolean operators:
Expands and retrieves any or all of the search terms [Example: heart attack OR myocardial infarction]
|AND||Narrows and retrieves records with only both search terms [Example: blood pressure AND stroke]|
|NOT||Excludes designated second term, only retrieves records for first [Example: health reform NOT health policy]|
Example: (heart attack OR myocardial infarction) AND blood pressure
Medical Subject Headings (MeSH) are the NLM's standardized terms used to describe the topics covered in MEDLINE. Articles about a topic are tagged with the appropriate subject headings, if available, whether or not the exact words of that subject heading are used in the article. Articles will be tagged with a subject heading even if the article uses some synonyms, spelling variations (e.g., British spelling), or different word endings (e.g., plural). Keep in mind, mapping to subject headings is not perfect, so employing other search techniques is also useful.
Automatic term mapping may pick up some MeSH for your search terms, viewable in the search details. You can also use the MeSH database to discover MeSH and get more context and information about them. See the MeSH in MEDLINE/PubMed tutorial for more information.