Access time is the time from the start of one storage device access to the time when the next access can be started. Access time consists of latency (the overhead of getting to the right place on the device and preparing to access it) and transfer time.
The term is applied to both random access memory (RAM) access and to hard disk and CD-ROM access. For RAM access, IBM prefers the term cycle time. However, the use of access time for RAM access is common. Access time to RAM is usually measured in nanoseconds. Access time to a hard disk or CD-ROM is usually measured in milliseconds.