a teaching/research 'fellow' [=a graduate student who gets money in exchange for teaching/research]
He attended the concert with a 'fellow' student. [=someone who is a student, as he is]
He has always tried to be of service to 'his fellow man'. [=to other people]
(..) The sole supporter of a large family, they say. Well, can't anything be done for them? Stand back. Move aside. Stand back. I have you to thank for that. Oh! Oh, what a good fellow! What a good fellow. Did you like him? He's in love with Kitty. Oh. But we should be discussing you and Dolly. (..)2012 Anna Karenina