Controlled vocabulary legislate the use of predefined, authorised terms that have been preselected by the designer of the vocabulary, in contrast to natural language vocabularies, where there is no restriction on the vocabulary.
Wildcard (?) and Truncation (*) Symbols -- Use the wildcard and truncation symbols to create searches where there are unknown characters, multiple spellings or various endings. Neither the wildcard nor the truncation symbol can be used as the first character in a search term. The wildcard is represented by a question mark (?). To use the wildcard, enter your search terms and replace each unknown character with a ?. Truncation is represented by an asterisk (*). To use truncation, enter the root of a search term and replace the ending with an *.
Grouping terms together using parentheses -- Parentheses also may be used to control a search query. Without parentheses, a search is executed from left to right. Words that you enclose in parentheses are searched first. Why is this important? Parentheses allow you to control and define the way the search will be executed. The left phrase in parentheses is searched first; then, based upon those results, the second phrase in parentheses is searched.
Using Quotation Marks -- Typically, when a phrase is enclosed by double quotations marks, the exact phrase is searched.