Board Thread:Wiki discussion/@comment-4881935-20130327060139/@comment-4087140-20130327060713

I was the one to start using both radius and diameter. In essence, if there is a visible thing on which an area is centered (a champion, a banner, a ward, whatever), then use radius, because it's a distance from that thing. In all other cases, use diameter, because the center of the effect is purely conceptual.