Rotational Latency

Also called rotational delay, the amount of time it takes for the desired sector of a disk (i.e., the sector from which data is to be read or written) to rotate under the read-write heads of the disk drive. The average rotational latency for a disk is half the amount of time it takes for the disk to make one revolution. The term typically is applied to rotating storage devices, such as hard disk drives and floppy drives (and even older magnetic drum systems), but not to tape drives.