Please indicate Mathematics Subject Classification (MSC) sections in need of general revision, suggest specific additions and changes, or point out errors. Mathematical Reviews and Zentralblatt für Mathematik will carefully consider all feedback and use it in preparing their joint MSC revision to be used starting in 2020. The current version is MSC2010. There is an interactive TiddlyWiki form of the MSC2010. The drafts of the MSC2010 were publicly developed using a MediaWiki at this site, namely the MSCwiki, and PDF and other forms are available there.