A measurement that indicates the frequency of semi-oscillations (half turns) made by the balance wheel; usually measured in vibrations per hour (vph). Most high-frequency (or high-beat) mechanical movements vibrate between six and 10 times a second, or 21,600 vph and 36,000 vph respectively. (In comparison, a typical quartz movement vibrates about 235 million times an hour.) While there are many factors that influence a watch’s timekeeping accuracy, generally speaking, the more often a movement vibrates, the more accurate it will be.