fellow

one of a pair

“one eye was blue but its fellow was brown”

a man who is the lover of a man or woman

a person who is member of one's class or profession

“he sent e-mail to his fellow hackers”

a friend who is frequently in the company of another

an informal form of address for a man

“Say, fellow, what are you doing?”

a boy or man

“there's a fellow at the door”

a member of a learned society

“he was elected a fellow of the American Physiological Association”