A refiner (1) for refining fibrous material has a first refiner element (3, 5) and a second refiner element (3, 5). The second refiner element is arranged around the first refiner element in such a manner that the first refiner element and the second refiner element have a common middle axis (7) such that there is a refining space (8) between the first refiner element and the second refiner element. The first refiner element and/or the second refiner element are arranged to rotate around the middle axis and the refiner elements have refining surfaces (4, 6), through which the fibrous material is fed into or exits the refining space (8). The refiner has, in the direction of the middle axis of the refiner elements, at least two feed regions, through which the fibrous material to be refined is feedable into the refining space (8).