Many databases have a document, thesaurus or index describing their preferred or controlled vocabulary, which explains how the literature is organized.
In PubMed, the controlled vocabulary is called MeSH which stands for Medical Subject Headings. The MeSH thesaurus can be accessed through PubMed, by either clicking on the advanced option under the search box OR by scrolling to the bottom of the PubMed webpage and locating the MeSH database
In CINAHL, the controlled vocabulary is called CINAHL Subject Headings. The CINAHL Subject Headings can be accessed through CINAHL and is located on the top toolbar.
