 Many databases use a controlled vocabulary to categorize papers on a particular topic together. Searching by a controlled vocabulary will only return papers that are on that topic. PubMed's controlled vocabulary is called MESH, sort for medical subject headings. You can search the MESH database to locate terms. The MESH database is linked off the PubMed homepage. Type in a term related to your topic. For my topic, I'm interested in prosthetic lower lints. I'll first find a MESH term for prostheses. Your best matches appear at the top of the results. Each result also has a definition provided. You can check the box next to the term to add the MESH to your search builder. Click on a term to go to the full record. The full MESH record shows PubMed search options for this term. There are various subheadings available that will help narrow down by subtopic. You can check any of these if they are relevant to your topic. Add them to the search builder. Search builder does allow you to use Boolean operators to combine and remove concepts. Lastly, at the bottom is a complete mapping of the MESH term, which can sometimes be helpful to you to find more MESH to search by. Above the MESH term are more broad concepts while below will be more narrow. For my topic, I am seeing artificial limbs as an additional MESH term. I can then click it and repeat the process to add terms to the search builder. You can continue to search for MESH in the database and add terms to the search builder. When you are finished, you can search PubMed to view the results. This was a quick overview of MESH. If you need assistance with MESH, PubMed, or any other library resources, don't hesitate to reach out and ask a librarian.