… Friendship arises the same way. For us of course the shared activity and therefore the companionship on which Friendship supervenes will not often be a bodily one like hunting or fighting. It may be a common religion, common studies, eight common profession, even a common recreation. All who share it will be our companions; but one or two or three who share something more will be our Friends.
“Friendship” in The Four Loves, C. S. Lewis