length of time that a data storage device, associated with a computer, takes to process and return data from the time of the original request for the data.

1. time taken by a computer or automated typewriter to locate data or an instruction word in its memory (storage) and transfer it.
2. time taken to transfer information from a computer or automated typewriter to the location in that device where it will be stored.

the amount of time needed by a memory device to transfer data to the CPU.