Enhanced MeSH® Browser

a new feature has been added to the Descriptor display in the MeSH Browser. Previously, the past display of a given Descriptor consisted of the Descriptors terms and other data elements. Now there is the additional option of viewing the "Concept Structure" of the record as it exists in XML MeSH (see Files available to download.)
The concept structure view groups synonymous terms into concepts. For example, the terms "Cardiomegaly" and "Enlarged Heart" are synonymous and so belong in the same concept. Every Descriptor record has at least one concept and every concept has at least one term. For further information see Concept Structure in XML MeSH.
The "Standard" Concept View provides the minimum concept structure, with terms and scope notes. The "Expanded" Concept View provides additional concept and term attributes, such as Concept UI, Semantic Type, and Lexical Tag. Definitions of these attributes are given in the list of XML MeSH Data Elements, where the "MeSH Browser" label is given for every applicable element.

Johnston, D. Enhanced MeSH® Browser. NLM Tech Bull. 2007 Sep-Oct; (358):e8.