San'indō (山陰道) is a Japanese geographical term. It means both an ancient division of the country and the main road running through it. San'in translates to "the shaded side of a mountain", while dō, depending on the context, can mean either a road, or a circuit, in the sense of delineating a region. This name derives from the idea that the northern side of the central mountain chain running through Honshū was the "shaded" side, while the southern side was the "sunny" (山陽 San'yō) side. The pre-modern region corresponds for the most part with the modern conception of the San'in region.