(1) Because the tonearm of a record player is pivoted at the stationary end, the stylus moves across the record in an arc and meets the groove at an ever-changing angle. The cutting stylus, however, moves in a straight line, always 90˚ to the groove direction. This condition is called tracking error.
(2) An error which occurs in disk drives when the read/write head cannot be placed accurately over the data blocks due to a misalignment in the head servo, a defect in the recording medium, or a misalignment in the recording process. Also, a similar error in CD player mechanisms.