WATER RESISTANT or WATERPROOF

Water resistance is an important feauture of any timepiece and is usually measured in increments of one atmosphere (atm or bar, equal to 10 meters of water pressure) or meters and is often noted on the dial or caseback.The case is designed in such a way to resist infiltration by water (3 atmospheres, corresponding to a conventional depth of 30 meters; 5 atmospheres, corresponding to conventional depth of 50 meters.)

WHEEL
Circular element, mostly toothed, combines with an arbor and a pinion to make up a gear. Wheels are normally made of brass, while arbors and pinions are made of steel. The wheels betwen barrel and escapement make up the so called train.

WINDING STEM
Element transmitting motion from the crown to the gears governing manual winding and setting.

WINDING, AUTOMATIC VIBRATION
Movement of the pendulum or other oscillating bodies, limited by two consecutive extreme positions. In an alternate (pendulum or balance) movement, a vibration is a half of an oscillation. The number of hourly vibrations corresponds to the frequency of a watch movement, determined by the mass and diameter of a balance and the elastic force of the balance spring. The number of vibrations per hour (vph) determines the breaking up of time ( the "steps" of a second hand). For instance, 18,000 vph equals a vibration duration of 1/5 second; in the same way 21,600 vph = 1/6 second; 28,800 vph = 1/8 second; 36,000 vph = 1/10 second. Until the 1950s, wristwatches worked mostly at a frequency of 18,000 vph; later, higher frequencies were adopted to produce a lower percentage of irregularities to the rate. Today, the most common frequency adopted is 28,800 vph, which assures a good precision standard and less lubrication problems than extremely high frequencies, such as 36,000 vph.

WINDOW
Aperture in the dial, that allows reading the underlying indication, mainly the date, but also indications concerning a second zone's time or jumping hour.

WORLD TIME
Additional feature of watches provided with a GMT function, displaying the 24 time zones on the dial or bezel, each zone referenced by a city name, providing instantaneous reading of the time of any country.