When a user performs a basic search in a database, they are using what are known as keywords. While keywords are a great way to start a search, a user could also search with terms provided by the database, which is known as controlled vocabulary.
Controlled vocabularies are standardized, organized sets of terms that databases use to describe content in a consistent fashion. Many databases have their own, unique controlled vocabulary, as demonstrated in the tutorials in the table below.
| Database | Controlled Vocabulary Name | Tutorial |
|---|---|---|
| CINAHL | CINAHL Subject Headings | Using CINAHL/MeSH Subject Headings |
| EMBASE | Emtree | Searching in Embase |
| PsycInfo | Thesaurus | APA Thesaurus of Psychological Index Terms |
| Pubmed | MeSH | Foundations of MeSH in Medline/Pubmed |
Often controlled vocabulary terms are applied to content by metadata specialists, such as those working for the National Library of Medicine. Compared to keywords, controlled vocabulary terms usually generate fewer but more relevant results. However, a user must use the exact term.
Example situations:
- If the initial keyword search returned too many or too few results, try controlled vocabulary terms.
- If a researcher is doing a comprehensive search (e.g., a systematic review), combine both keywords and controlled vocabulary terms to increase the number of resources retrieved.
- If a user is looking for background information, a keyword search generally suffices.