The invention concerns a sail (1) for a wind-powered vehicle, such as a surfboard, sailing boat or the like, wherein the sail (1) can be connected along its front edge (11) to a mast (3). At its clew or at or near its lower edge (16) the sail (1) can be connected at least at points to a boom (30) which is connected in hinged manner to the mast (3). In the region of its free rear edge (12) the sail (1) comprises at least one part (20) which is adjustable in the sail plane. By adjusting the sail part (20) in its one adjusting direction, the overall area of the sail (1) can be decreased and, by adjusting the sail part (20) in its other adjusting direction, the overall area of the sail (1) can be increased. The sail according to the invention is characterized in that the adjustable sail part (20) can be displaced substantially perpendicular to the free rear edge (12) of the sail (1) and/or substantially parallel to the boom (30).