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Medical Sciences: Database Search Tips: Keywords vs. Subjects

Recommended resources for the College of Osteopathic Medicine

How to find terms

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). Ask Us for help using thesauri.

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.

What are subject headings and keywords?

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 Theatres" you will find nothing, as they are listed under the subject heading "Theatres - Movies."

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

Here are some key points about each type of search:


  • natural language (conversational) describing your topic - good place to start your search 
  • pre-defined "Controlled Vocabulary" or higher order terminology 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
  • Broadens your search providing more results. But may yield too many or too few results
  • Narrows your search providing fewer results. If search yields too many results - use a subheading to focus on one aspect of the broader subject
  • may yield many irrelevant results
  • Examples:


    Skin Cancer

    High Blood Pressure


  • results usually very relevant to the topic
  • Examples:


    Skin Neoplasms



When you search a database and do not get the results you expect, Ask Us for advice.

Keyword v Controlled Vocabulary Searching

A controlled vocabulary is a standardized, pre-defined set of terms used by a database to describe and categorize articles or sources of information based on content. Controlled vocabularies can also be referred to as Subjects, Subject Headings, Subject Terms, Descriptors, Thesaurus, or Index terms. 

Using a variety of both keywords and controlled vocabulary when searching library databases will help you retrieve the best search results!

Each database handles controlled vocabulary differently including the terminology.The following video explains the meaning and functionality of controlled vocabulary.