There are two ways to use search terms in PubMed: as keywords and as subject terms--specifically called Medical Subject Headings (MeSH) in PubMed. MeSH allows you to search by topic and by meaning, rather than just matching text words that may or may not represent the topic you are researching.
To get started with MeSH, click the MeSH Database link at the bottom right of the PubMed homepage.
On this next page you can search for the topic you are interested in. Note, that this page retains the old look of PubMed. As you type in you concept PubMed will populate the search box with suggestions for concept matches.
The results of your search will start with the best match. In the image below, if you search for cancer PubMed will show that Neoplasms is the MeSH term for that concept. You can add it to your search with the box on the right, or click on Neoplasms to get more information about the entry.
When you open Neoplasms you will get a wealth of details on the term. Some of this is basic information such as the definition and entry terms. You will also see options for focusing your search such as Subheadings and Restrict to MeSH Major Topic.
If you scroll further down in the entry you will see a hierarchy of subject terms. This can help you focus your search more broadly or more narrowly. Some MeSH terms appear in multiple hierarchies.
