• Search Queries
• MeSH Term Index
• MEDLINE Character Database
• Special Characters Converted for Indexing

Search Queries
PubMed queries that include the following characters are translated as follows:

parentheses ( ) - used to create Boolean nesting
square brackets [ ] - search field tag qualification
ampersand & - Boolean operator AND
pipe | - Boolean operator OR
forward slash / - used to define MeSH/Subheading combinations
comma , - typically forces a space, e.g., a,b is translated to a, b
colon : - designates a range operation
double quotes " - used to force a phrase search
pound sign # - designates an Entrez History search statement number when immediately followed by a number, e.g., #1 AND cat
asterisk * - used as a wildcard symbol for search term truncation, e.g., toxicol*

The following characters are converted to spaces in PubMed search queries:

! exclamation mark
# pound sign
dollar sign $
percentage sign %
asterisk *
plus symbol +
minus symbol -
period .
semi-colon ;
angle brackets < >
equal sign =
question mark ?
backslash \
carrot ^
underscore _
curly brackets { }
approximately ~

MeSH Term Index:

• During indexing for MeSH terms that include an ampersand, such as administration & dosage, the ampersand is translated to 'and'.
• The forward slash is used to define MeSH/Subheading combinations, e.g., neoplasms/therapy