I am curious whether there are PhD students in this forum who'd like to give their take on this matter. How important is learning a foreign language (French, German, or Russian) in a mathematical career in this modern age? My interests are in applied analysis (diff equations) and connections to probability and am concerned whether learning French would be of great value. My focus is on applied math but I'd love to study the theory in depth. The school I've been admitted to so far does not impose a language requirement for the completion of the PhD degree.
I am wondering if, among those of you who have taken language courses during your PhD program, you remember anything you learned due to lack of practice. After all, there really arent courses like French for Math PhD students in a university, it's most probably a general language course. It is inevitable that you'll forget most of it after not being able to practice it...So is it worth it?