A (widely accepted) way of assigning versions to softwares or libraries such that change in version number carries a semantic message regarding the underlying API design.

• A version consists of 3 numbers with periods in between: X.Y.Z where each has a name as follows:
  • X: “major”
  • Y: “minor”
  • Z: “patch”

• An increase in Z indicates an API-unrelated update or a bug fix. There is no API change and thus no reason for the user to update his/her code.

• An increase in Y indicates a backward-compatible API change. A user can choose to update his/her code accordingly, but the code doesn’t break either way.

• An increase in X indicates a breaking change in API, i.e. backward compatibility is not guaranteed anymore. A user has to adapt his/her code to the changed API so to use the given version of software or library.

References:

• https://apifriends.com/api-management/what-is-semantic-versioning/