Like programming languages, it depends on the context. “Learned” in a casual conversation would mean that one can write programs/libraries and achieve what they want in that language. “Learned” in a more professional manner, like a resume, would mean you can write good, maintainable code and know much of the language underlying stuff and other tools. But practically, in my experience, on a job, knowing a language/library means being better than or equal to your boss if they’re a dev.

The boss of my father, for example, is gonna challenge you with his knowledge until you agree you’re wrong, if you claim you “know” something. To him, “knowing” would mean you read the docs, source code and used it for many years, so actually know all quirks known to mankind of that language/library. Which isn’t really humanly possible.