Lesson
Sometimes it is more efficient to search by subject headings than by keywords. Most online databases have a list of the correct subject headings to be used. This list is sometimes called controlled vocabulary. The Library of Congress Subject Headings, for example, are the "official" headings used in library catalogs for describing the focus of each book. Here’s what our topic — gun control — looks like in the Library of Congress Subject Headings:
Gun control (May Subd Geog)
[HV7435-HV7439] Here are entered general and non-legal works on the control of guns. Works on the legal aspects of gun control are entered under Firearms — Law and legislation. UF
Control of guns
Firearms control
Handgun control
BT
Firearms — Law and legislation
To understand the above you need to know what the abbreviations refer to. UF is the abbreviation for "Use For" and means that instead of using "Control of Guns," "Firearms control," or "Handgun control," you should use the term "Gun control." BT is the abbreviation for "broader term." You can see that "firearms" encompasses more than "gun control" and therefore if you used firearms instead of gun control, you would be doing a broader, less concise search.
Some other abbreviations you might find include:
RT, the abbreviation for a "related term," which you might use for broader searching.
NT, the abbreviation for "narrower term," which you could use for more precise searching.
The list of subject headings for a given database is called a thesaurus. If the database you’re using has a thesaurus, take advantage of it to find correct and alternate terms. Using these specific terms, also called "controlled vocabulary" or "descriptors," is an excellent method of precision searching.