What makes you an expert in a programming language

How would you define expertise in a programming language?

Is it knowledge of all the mechanics and advanced concepts of the language? Or is it based on the number of functional projects you’ve built?

There might be a situation where you know enough about a language to complete a variety of tasks without necessarily knowing some deep aspects because you never needed them. Does this qualify you for the title of ‘expert’? Or do you need to know sufficient libraries and paradigms of the language to be considered one?

It’s just like speaking a human language. Some people can speak English but still fail English exams, sure you don’t qualify as a professor, but compared to a non-native speaker who is trying to learn, you’re really good!

Maybe being an expert is relative. Maybe being an expert is not a destination, but a never ending journey. Maybe the answer to this question is really how many questions you’ve answered on Stack Overflow 😅.

What do you think? Are you an expert?