Although command terms and characters vary in electronic databases and Web search engines, some common functions are listed here:
- Use quotation marks around words that are part of a phrase: "gateway drug."
- Use AND to connect words that must appear in a document: hyperactivity AND children. In some search engines--Google, for example--AND is assumed, so typing it is unnecessary. Other search engines require a plus sign instead: hyperactivity + children.
- Use NOT in front of words that must not appear in a document: Persian Gulf NOT war. Some search engines require a minus sign (hyphen) instead: Persian Gulf -war.
- Use OR if only one of the terms must appear in a document: "mountain lion" OR cougar.
- Use an asterisk as a substitute for letters that might vary: "marine biolog* (to find marine biology or marine biologist, for example).
- Use parenthesis to group a search expression and combine it with another: (standard OR student OR test*) AND reform.
NOTE: Many databases and search engines offer an advanced search option for refining your search with filters for exact phrases that must appear, specific words that should not appear, date restrictions, author and title restrictions, and so on.