The independent swell or waves in the wave spectrum, which have originated from the same storm or fetch of wind, and are moving in the same direction. At a single location like a buoy, there may be a combination of different wave trains present, which have each originated from separate areas of generation. As an example, there may be a swell from the South, a swell from the West, and a local wind wave out of the Northeast. Each of these wave events are separate wave trains, which combine to constitute the wave spectrum at that location.