See this visual explanation of Boolean Searching from Nicholls State University.
Boolean Operators help you define the set of results you want the database to show you.
AND — displays results that have both the terms searched for. This is a narrower search.
Example: If you have 15 items (5 cat, 5 dog, 5 cat & dog), a search for cat AND dog will bring up results for books and articles that have both "cat" and "dog" in them: 5 results.
OR — displays results that have at least one of the terms searched for. This is a broader search.
Example: If you have 15 items (5 cat, 5 dog, 5 cat and dog), a search for cat OR dog will bring up results for books and articles that have either "cat" or "dog" in them: 15 results.
NOT — a way of excluding something. The term that comes after NOT is excluded. This is a narrower search.
Example: If you have 15 items (5 cat, 5 dog, 5 cat and dog), a search for cat NOT dog will bring up results for books and articles that have "cat" in them but excludes results that have "dog" in them: 5 results.
Using wildcards is a way to expand your search possibilities. Instead of adding multiple lines of search fields, wildcards can collapse those into one. These techniques work in most databases (but not all). There are no wildcard options in Science Direct.
Wildcards — a symbol used to represent any 1 character. Use # symbol or sometimes * symbol.
Wildcards can usually be used 1) at the end of a word or 2) within a word to search variant spellings of a word. See Truncation for a technique to represent more than 1 character. You can use more than one wildcard symbol to stand in for more than one character.
Example: wom#n retrieves woman or women
Using truncation is a way to expand your search possibilities. Instead of adding multiple lines of search fields, truncation can collapse those into one. These techniques work in most databases (but not all). There are no truncation options in Science Direct.
Truncation — a symbol added to the end of the root of a word to instruct the database to search for all forms of a word. Use the * symbol in most databases.
Example: adolescen* retrieves adolescent, adolescents, or adolescence