text: user3015: Medical Subject Headings (MeSH) is a very comprehensive vocabulary to index the biomedical literature on Medline or PubMed (which is the major Biomedical literature database). MeSH is arranged into Descriptor > Concept > term hierarchy, but I still do not understand the difference between a MeSH descriptor and a MeSH concept.
  For example, for Knee
  
  MeSH descriptor is D007717 
  MeSH concept is M0012066 (Under the concepts section in the link)
  
  Even after reading the description here and here, I am still not sure about the purpose of MeSH concept and MeSH descriptor. 
  Could anyone please shed some light on it?
  
  user3015: MeSH is organized into Descriptor > Concept > Term hierarchy, where all the synonymous <term>'s are grouped together under a <concept>. For example, consider the MeSH terms,
  
  Blood-Brain Barrier
  Hemato-Encephalic Barrier
  Brain-Blood Barrier
  
  All these terms are group under the umbrella concept of "Blood-brain barrier".
  
original_text: 3015: <p>Medical Subject Headings (MeSH) is a very comprehensive vocabulary to index the biomedical literature on Medline or PubMed (which is the major Biomedical literature database). MeSH is arranged into Descriptor > Concept > term hierarchy, but I still do not understand the difference between a MeSH descriptor and a MeSH concept.</p>
  
  <p>For example, for Knee</p>
  
  <ul>
  <li>MeSH descriptor is <a href="https://meshb.nlm.nih.gov/record/ui?ui=D007717" rel="nofollow noreferrer">D007717</a> </li>
  <li>MeSH concept is <a href="https://meshb.nlm.nih.gov/record/ui?ui=D007717" rel="nofollow noreferrer">M0012066</a> (Under the concepts section in the link)</li>
  </ul>
  
  <p>Even after reading the description <a href="https://www.nlm.nih.gov/mesh/concept_structure.html" rel="nofollow noreferrer">here</a> and <a href="https://www.nlm.nih.gov/mesh/xmlmesh.html" rel="nofollow noreferrer">here</a>, I am still not sure about the purpose of MeSH concept and MeSH descriptor. </p>
  
  <p>Could anyone please shed some light on it?</p>
   3015: <p>MeSH is organized into <code>Descriptor &gt; Concept &gt; Term hierarchy</code>, where all the synonymous <code>&lt;term&gt;</code>'s are grouped together under a <code>&lt;concept&gt;</code>. For example, consider the MeSH terms,</p>
  
  <ol>
  <li>Blood-Brain Barrier</li>
  <li>Hemato-Encephalic Barrier</li>
  <li>Brain-Blood Barrier</li>
  </ol>
  
  <p>All these terms are group under the umbrella concept of "<a href="https://meshb.nlm.nih.gov/record/ui?ui=D001812" rel="nofollow noreferrer">Blood-brain barrier</a>".</p>
  