As the days went by, the evolution of like into love was accelerated.  White Fang himself began to grow aware of it, though in his consciousness he knew not what love was.  It manifested itself to him as a void in his being—a hungry, aching, yearning void that clamoured to be filled.  It was a pain and an unrest; and it received easement only by the touch of the new god’s presence.  At such times love was joy to him, a wild, keen-thrilling satisfaction.  But when away from his god, the pain and the unrest returned; the void in him sprang up and pressed against him with its emptiness, and the hunger gnawed and gnawed unceasingly.
Jack London
like, love, passion