What feature distinguishes an automatic watch?

An automatic watch is renowned for its ability to self-wind through the natural motion of the wearer's wrist. This mechanical system utilizes a rotor, which moves as the wearer moves, thereby winding the mainspring and powering the watch. This characteristic is essential to automatic watches as it eliminates the need for manual winding, characteristic of traditional mechanical watches.

In contrast, the other features do not apply to automatic watches. Digital displays and plastic materials are generally associated with quartz watches, while battery operation is not applicable to automatic watches, as they are powered by mechanical movements. The self-winding feature is fundamental to understanding the functionality and appeal of automatic timepieces, showing how they harness kinetic energy for continual operation without the need for external power sources.