Self-winding refers to a watch mainspring that is wound automatically by a device inside the watch that rotates during normal wrist motion.

see Automatic above, which is the preferred term.

This term refers to a mechanically powered watch that is wound by the motion of the wearer's arm rather than through turning the winding stem ( manual mechanical ). In response to this motion, a rotor turns and winds the watch's mainspring. Most automatic watches have up to 36 hours of power reserve. If an automatic watch is not worn for a day or two, it will wind down and need to be wound by hand to get it started again. Click here for automatic watch instructions .

An informal name for a perpetual watch.