Abstract: A refiner segment for refining lignocellulosic material, has a surface including a plurality of bars extending along a direction between an inner periphery of the refiner segment and an outer periphery of the refiner segment, and a plurality of dams, each of the plurality of dams extending between a corresponding pair of adjacent bars among the plurality of bars, wherein at least one of the plurality of dams is a three-dimensionally extending body including three sides, the three-dimensionally extending body extends between the corresponding pair of adjacent bars and includes a curved side, forming one of the three sides, facing the inner periphery of the refiner segment, the curved side having a concave curvature with regard to the inner periphery to thereby form a rounded section in an area defined by the at least one of the plurality of dams and the corresponding pair of adjacent bars.