According to the standard:
Given a version number MAJOR.MINOR.PATCH, increment the: MAJOR version when you make incompatible API changes, MINOR version when you add functionality in a backwards-compatible manner, and PATCH version when you make backwards-compatible bug fixes. Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.
While in alpha TiddlyWiki5 uses the pre-release label "alpha", for example:
Each new alpha or beta release will bump the
PATCH version number. This breaks the strict semantics of versioning because
PATCH increments are supposed to be reserved for compatible changes.
Note that prior to 5.0.1-alpha, TiddlyWiki5 used version numbers formatted as 5.0.0-alpha.19. The change was made to enable the upgrade mechanism to recognise plugin updates from the version information.
During development when a new release is being prepared, the pre-release label is set to
TiddlyWiki5 uses the version information attached to plugins for determining which of two plugins is more recent during an upgrade or import. The pre-release label is ignored when performing these comparisons.