when there is one.
* Momentary Mark:: Enabling Transient Mark mode momentarily.
* Using Region:: Summary of ways to operate on contents of the region.
-* Selective Undo:: Undoing within a given region.
* Marking Objects:: Commands to put region around textual units.
* Mark Ring:: Previous mark positions saved so you can go back there.
* Global Mark Ring:: Previous mark positions in various buffers.