A person who is not formally enrolled as a student, researcher or faculty in some university or college but who takes interest in exploring academic topics/stuff. For e.g. Such a person could be someone who is working in the corporate & has interest in & explores his academic fields. What could be a simple, 'easy for all to understand' term to refer to this person?
I believe there is, perhaps, no easy single word for that, I can accept answers which propose a phrase that can describe this in a short and better way (must be easy for anyone to understand).
A not-so-good example: "A learner or academic enthusiast".