Seek time is one of the three delays associated with reading or writing data on a computer's disk drive, and somewhat similar for CD or DVD drives. The others are rotational delay and transfer time, and their sum is access time. In order to read or write data in a particular place on the disk, the read/write head of the disk needs to be physically moved to the correct place. This process is known as seeking, and the time it takes for the head to move to the right place is the seek time. Seek time for a given disk varies depending on how far the head's destination is from its origin at the time of each read or write instruction; usually one discusses a disk's average seek time.
