Syncopation is, essentially, displacing single beats within given meters. For example, if you play a regular back beat and from time to time suddenly shift your kick or snare from their given position, but they all remain within the meter – that’s a syncopation. With polyrhythm, you play two rhythms simultaneously, but within these rhythms, the timing remains precise. Of course, the two can be combined, but playing polyrhythm with deliberate offbeat is an art.