Versions for plugins/themes/app:

We follow WordPress versioning philosophy: vA.B.C (ie: 4.3.1).

A: is for major version. At least 30% of the source code has been changed or the UI has drastically changed, the user will be able to figure out in a few minutes that this is a new version.

B: is for new features update. This version brings at least 1 new feature.

C: is for bug fixes and minor improvements.

Versions for our WordPress website repos:

We will use the WordPress version number. However since we may need to deploy multiple versions during one WordPress version. We add a D version number : vA.B.C.D where A, B and C correspond to WordPress the version and D is our internal version (with 3rd party themes and plugins as well as in-house sub-modules).