How do version numbers work for MRI Ruby?

Question

A recent question, \"What happened with Ruby 1.9.2?\", made me wonder about version numbers for MRI Ruby mean.

The scheme MRI Ruby uses differs from that of semver.o

Answer 1

They have changed to quasi-semantic versioning starting with Ruby 2.1.0. See https://www.ruby-lang.org/en/news/2013/12/21/semantic-versioning-after-2-1-0/ for further details, but the version numbers will now have the following meaning:

MAJOR: increased when incompatible change which can’t be released in MINOR
    Reserved for special events
MINOR: increased every christmas, may be API incompatible
TEENY: security or bug fix which maintains API compatibility
    May be increased more than 10 (such as 2.1.11), and will be released every 2-3 months.
PATCH: number of commits since last MINOR release (will be reset at 0 when releasing MINOR)

Answer 2

(Here the terms differ from the classic semver.org where 2.0.0 is composed of MAJOR.MINOR.PATCH: The ruby scheme, as illustrated in version.h or test_gem.rb, is more V2.0.0pxxx, as in MAJOR.MINOR.TEENY.PATCHLEVEL)

• Major seems to be reserved for language changes, as illustrated by Ruby2.0.0 Change Logs.
• Minor used to have a different meaning than today, from the article on 1.9 release (December 2007):

Previously, a version number for Ruby with an odd minor version number signified an experimental version. So Ruby 1.7 was experimental, while Ruby 1.8 was a production version.
The Ruby core team has changed this so that, with the advent of Ruby 1.9.0, Ruby 1.9 is no longer considered experimental, although it may be a while before the implementation becomes ready for production use

Today, a minor version contains semantic differences:

On the other hand, Ruby 1.9 is not completely backward compatible with Ruby 1.8. Some of the semantics have changed. For example, block arguments are now local to the block, and there are subtle changes to block semantics.The changes mean that many existing Ruby programs will need some amount of conversion to take advantage of Ruby 1.9.

• teeny (like 1.9.2) adds new features

• patchlevel is more about a build number, adding internal fixes, security fixes, promoting a ruby version to "production level" (as that was the case for 1.9.2-p290)