Abbreviation for Constant Linear Velocity. This is a term used to characterize disc-based media. The idea of CLV is to maintain the same (constant) amount of surface area passing by the read/write mechanism (whether Laser or magnetic) at all times. This means a CLV drive must slow down the rotational speed of the disc as the reading or writing of data moves towards the outside of the disc to counteract for the physical reality that any rotating disc has a higher linear velocity at the outside than the inside. Devices that use constant rotational velocity (instead of CLV) can theoretically read and write faster at a given maximum rotational velocity. A few examples of media that are based on CLV are all major forms of CD and DVD. A major disc format that does not use CLV is magneto optical (MO).