Once you've identified your search terms and synonyms, the final prepatory step is to connect those terms into a search phrase.
Online search tools like the library catalog and article databases require a specific format for search phrases, including the use of what are called Boolean operators. Boolean operators are the words AND, OR, and NOT. Placing these words between your search terms will help you find books and articles that are targeted to your research topic.
For searching the catalog, the Boolean operator AND gives you more targeted results by requiring that two or more terms all appear within the title, abstract, subject terms or table of contents of a book's catalog record. When searching article databases, the AND operator works the same as in the catalog but also searches within the full-text of articles, if available.
For example, a keyword search in the library catalog for "politics" returns 32,000 titles. A keyword search for "politics" AND "climate change" brings the results down to 109 titles. A keyword search for "politics" AND "climate change" AND "perception*" returns only 6 titles, all of which are relevant to the topic.
Wilcard: You probably noticed the use of "*" at the end of the word "perception" in the last example. The "*" is an example of a wildcard. The library catalog and many of the online databases allow you to use wildcards to truncate your search terms. When you use a wildcard, the catalog or database will search for all forms of the word after the "*". For example "politic*" will search for politics, political, politician, politicized, etc.
The Boolean operator OR is the opposite of AND. OR generally gives you more search results by requiring either one term or another to appear in a book or article. OR works best when you are looking for synonyms or related terms.
For example, a keyword search in the library catalog for "climate change" returns 1,851 titles.
A keyword search for "climate change" OR "global warming" returns 2,522 titles.
In many cases, the best time to use OR is within a longer search phrase, for example:
politics AND (climate change OR global warming) AND opinion = 1 retrieved title