What does “Automatic” mean?

An automatic, or self-winding, watch has a mechanical movement that winds itself through the motion of the wearer's wrist. A weighted rotor inside the movement turns as the wrist moves and winds the mainspring through a set of gears. Rolex introduced its Perpetual rotor in 1931, and today most luxury mechanical watches are automatic.

An automatic watch still needs to be worn regularly, or wound, to keep running; left unworn, it stops once the power reserve runs out, and most can also be wound by hand through the crown. Buyers often ask about the power reserve and whether the watch keeps good time. Like all mechanical watches, automatics need periodic servicing at the intervals the brand recommends. A winding problem, such as a noisy rotor or a watch that doesn't stay wound when worn, is something to check before buying.

Example: 'Automatic movement running well, keeping good time.'