clone:    An exact digital replica of the original data at a point-in-time. Created by associating the source and destination device and then synchronized by copying from original data, typically in units equal to one or more multiples of the default information unit used in the device, i.e., byte, block, track, or extent. The synchronization process continues until the copy relationship is broken by splitting the two images at a point-in-time. Unlike a split mirror point-in-time copy, the original and clone typically do not maintain a record of changes, so as a result, a clone, while a copy, could not be used for an optimized restore or re-silvering because either member would not have knowledge of changes made, and therefore, a differential restore is not possible, rather a full copy is needed.

Note: there is much vendor variance not covered in this definition.