Markdown Extra is a lightweight markup language based on Markdown implemented in PHP (originally), Python and Ruby. It adds features not available with plain Markdown syntax. Markdown Extra is supported in content management systems, for example Drupal, TYPO3 and MediaWiki. It adds the following features to Markdown: * Markdown inside HTML blocks * Elements with id/class attribute * Fenced code blocks * Tables * Definition lists * Footnotes * Abbreviations