What does FELLOW mean?

noun

1. a boy or man“that chap is your host”
2. a friend who is frequently in the company of another“drinking companions”
3. a person who is member of one's class or profession“the surgeon consulted his colleagues”
4. one of a pair“he lost the mate to his shoe”
5. a member of a learned society“he was elected a fellow of the American Physiological Association”
6. an informal form of address for a man“Say, fellow, what are you doing?”
7. a man who is the lover of a girl or young woman“if I'd known he was her boyfriend I wouldn't have asked”