Companionship, n.
Fellowship; association; the act or fact of keeping company with any one. Shak. He never seemed to avail himself of my sympathy other than by mere companionship. W. Irwing
Shades of meaning
Fernald has no entry of its own for companionship; he lists it under acquaintance, association.
Where he writes about it:
There may be pleasant acquaintance with little companionship; and conversely, much companionship with little acquaintance, as between busy clerks at adjoining desks. — from acquaintance
Friendship includes acquaintance with some degree of intimacy, and ordinarily companionship, though in a wider sense friendship may exist between those who have never met, but know each other only by word and deed. — from acquaintance
Fellowship involves not merely acquaintance and companionship, but sympathy as well. — from acquaintance