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Hamersly Library

Database Search Tips: Keywords vs. Subjects

What to Look For

To find subject headings for your topic:

  • Look to see if the database has an online thesaurus to browse for subjects that match your topic (check the Help screens).
  • Some databases publish thesauri in print (e.g. Thesaurus of Psychological Index Terms for the PsycInfo database). 


Another way to find subject headings:

  • Start with a keyword search, using words/phrases that describe your topic.
  • Browse the results; choose 2 or 3 that are relevant.
  • Look at the Subject or Descriptor field and note the terms used (write them down).
  • Redo your search using those terms.
  • Your results will be more precise than your initial keyword search.

 

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What are Keywords and Subject Headings?

Keyword searching is how you typically search web search engines.  Think of important words or phrases and type them in to get results.

Subject Headings describe the content of each item in a database. Use these headings to find relevant items on the same topic.  Searching by subject headings (a.k.a. descriptors) is the most precise way to search article databases.

It is not easy to guess which subject headings are used in a given database. For example, the phone book's Yellow Pages use subject headings. If you look for "Movie Theaters" you will find nothing, as they are listed under the subject heading "Theaters - Movies."

Here are some key points about each type of search:

Keywords
vs.
Subject Headings
  • natural language words describing your topic - good to start with
 
  • pre-defined "controlled vocabulary" words used to describe the content of each item (book, journal article) in a database
  • more flexible to search by - can combine together in many ways
 
  • less flexible to search by - need to know the exact controlled vocabulary term
  • database looks for keywords anywhere in the record - not necessarily connected together
 
  • database looks for subjects only in the subject heading or descriptor field, where the most relevant words appear
  • may yield too many or too few results
 
  • if too many results - also uses subheadings to focus on one aspect of the broader subject
  • may yield many irrelevant results
 
  • results usually very relevant to the topic

Content created by MIT Libraries, available under the Creative Commons Attribution Non-Commercial License.