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 called Boolean searching using the operators AND, OR, NOT.
For example, a search for history AND medicine will return items that contain both of the concepts:
medicine OR "public health" returns items that contain either one of the terms or both:
america NOT latin returns items that discuss the United States but do not mention Latin America:
Enclose phrases in quotations marks. This is an important strategy for getting exact results when searching phrases (e.g., "yellow fever"") or conducting known-item searches for titles ("Medical Progress and Social Reality") .
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, politicians, and so on.
Wildcard searches are for differences within words: a search for wom?n will return results for woman, women, and womyn.
When pairing two or more keywords with another keyword, it is important to "nest" the former terms within a larger Boolean search.
For example, (medicine OR medical OR health*) AND (history) AND ("united states" OR america*) will return results for the union of the three subject areas.