Resolution defines the smallest measurement that can be made, and thus defines the smallest position increment possible. Accuracy is how the system moves relative to perfect motion. If we commanded a 100 mm move, did the system actually move 100mm ? The error is Accuracy. Repeatability is how well we can repeat a move. Using the 100 mm example, if we did 1000, 100 mm moves, and every time were within 100.5 +/- 0.1, the repeatability would be 0.1 and the Accuracy is 0.5 mm. It is also important to note that accuracy vs. position variation causes velocity variations of the moving object.