What are subject terms?
Subject terms, also called controlled vocabulary, are specific words that have been assigned by a database to describe each book or article within. Library databases use searchable thesauri to arrange these subject terms. You can also use thesauri for ideas on keywords to use in your database searches when you aren’t quite sure which keywords to try. Type in the term that best describes your topic and see what the thesaurus has that might better describe that topic and search with that word instead. Using the thesaurus can help you figure out which synonym to use, which spelling to use, or which combination of terms to use.
Since subject terms reflect the main focus of the book or article, searching by subject may be a quick way to narrow your results to a particular topic. However, subject searching should be used as a second step. Try a keyword search first, then see what subjects are recommended to you, or look at the subject headings for useful search results, as shown below. Try adding those to the keyword search, or searching the subjects alone.
Why is a thesaurus useful?
You can use a thesaurus to collect search terms, including synonyms, but also terms that are more commonly used by professionals and scholars within a field. These terms are discipline specific: you find the terminology used within a discipline, with the corresponding level of detail. For example: in the thesaurus of ERIC over 30 types of 'students' are identified. For a database for education research, that level of detail makes sense.
In a database with a thesaurus, you can search directly from the list of thesaurus terms which can save a lot of time in your searches, especially when you are first getting started with your investigation.
In this example with CINAHL, the Subject Heading functions like a Thesaurus; it's giving us the controlled vocabulary we need for certain topics and other suggestions based on that subject. In the search box, type in the keyword or phrase you are wanting to investigate.
We can see where our search returns and what recommendations the database makes for future searches. In this case, Pediatric Nursing is a subject that we can Explode or search as a Major Concept.
When you Explode a term, you create a search query that “explodes” the subject heading. The headings are exploded to retrieve all references indexed to that term as well as all references indexed to any narrower subject terms. When you select Major Concept for a term, you create a search query that finds only records for which the subject heading is a major point of the article. Searches are limited with specific qualifiers (subheadings) to improve the precision of the search, and limited to major subject headings indicate the main concept of an article.
At this stage you can use the "Search Database" button and add additional keywords and phrases to your subject search. However, scrolling to the end of your results list gives you an option to "Browse Additional Terms" which allows you to add additional subjects to your search using the database's controlled vocabulary.
Conducting an additional search brings you back to the regular subject heading page, but it also clarifies in the note that "the previous selected search terms are being retained." This confirms that our previous Major Concept and Explode subject of Pediatric Nursing will still be marked when we conduct this new search for Play Therapy.
In this search, Play Therapy is only available to search as a Major Concept. Checking this search adds it to our saved search. REMEMBER: if you are searching two unrelated subjects, be sure to combine your search with AND. If all of your listed subjects are similar in nature, you can use OR. When you are ready to search, select the "Search Database" button to conduct your search.
In our search, the subject headings from the database are listed; MM refers to our Main Concept search and the + indicates the Explode option. Using the "Advanced Search" will also allow you to add in keywords and phrases, and there are still many opportunities to narrow your results down further with the Refine Results options to the left of your list.