Abstract: Internal-combustion engine (1), comprising an engine housing (2), which has an interior space (3) with an inner wall (4), which section-wise corresponds to a segment of a circular cylinder and section-wise corresponds to a segment, which deviates from the form of a circular cylinder, wherein a rotary disc (5) is centrally rotatably mounted in the interior space (3) around an axis of rotation (6), and an intake area, a compression area, an ignition area, a working area and an exhaust area are formed, wherein the rotary disc (5) is designed substantially in the form of a circular cylinder, wherein said rotary disc (5) has two slots (8, 9) in the circumferential area (7), into each of which slots a sliding element (10, 31) is inserted, wherein each sliding element (10, 11) is able to move along the slot concerned (8, 9), and is moved along the slot concerned (8, 9) on rotation of the rotary disc (5), wherein the end of the first sliding element (10) facing away from the axis of rotation (6) is guided along the i