After a lengthy debate, the core Drupal system is moving to a new, more simple convention for its version numbers: there will only be 2 digits. For example, the forthcoming stable release will be version 5.0. The 5 represents the major revision of Drupal, and indicates what modules and themes will be compatible with it. The 0 is the patch level, and indicates that it will be the first release of this version of Drupal. Subsequent bug fixes and security patches will be released as 5.1, 5.2, and so on. New features will only be added to the next version of Drupal core, (the 6.0 release in this case). You can find out more about this topic by reading version numbers, policies and which version you should use.

The naming convention for the CVS branches used for core and contributions has also shifted to match this new numbering scheme. Previously, the 4.7.x series of Drupal core lived on the DRUPAL-4-7 branch. Now, once the code moves into the final stages of preparation for the stable release, there will be a DRUPAL-5 branch where the 5.x series will live. Modules, themes and translations that have been ported to this version of core will have a DRUPAL-5 branch, as well. More information about Drupal's use of CVS can be found at the handbook pages about CVS.

Drupal version: Drupal 5.x