Keywords allow you to construct a search that reflects multiple issues in your research question. Building sets of related concepts and looking for their overlaps gives you more relevant and precise results. This approach is also called Boolean searching using the operators (AND, OR, NOT).
For example, a search for enlightenment AND medicine will return items that contain both terms:
medicine OR health* makes a larger set concerning medical issues:
medicine NOT physician* returns items that discuss medicine without talking about doctors.
Phrase searching:
Enclose phrases in quotations marks. This is an important strategy for getting exact results when searching phrases (e.g., "black death") or conducting known-item searches for titles.
Nested Searching:
When pairing two or more keywords with another keyword, it is important to "nest" the related terms within a larger Boolean search.For example, ("great britain" OR france) AND medicine AND "18th century" will return results for medical content and any one (or both) of the parenthetical terms.
(Many catalogs or databases will have an "advanced search" option, which provides multiple search boxes to facilitate nested Boolean searching.)
Truncation and Wildcards:
Most catalogs and databases enable users to search variations of keywords by using truncation (*) or wildcard (e.g., ?, $, !) symbols.
For example, one could search for politic* to find poltic, politics, political, politician, and so on.
Wildcard searching works similarly: a search for wom?n will return results for both woman and women.