(in its upper course, Pravyi Sym), a river in Krasnoiarsk Krai, RSFSR; a left tributary of the Renisei. The Sym measures 694 km in length and drains an area of 31,600 sq km. It originates in and flows through swamps on the eastern edge of the Western Siberia Plain. It is fed predominantly by snow. There is a long high-water period. The mean flow rate 215 km from the mouth is 175 cu m per sec. The river freezes in October or early November, and the ice breaks up in May. The Sym is navigable for a distance of 265 km from the mouth.