Watch Terminology 101
Alarm: A device that sounds a signal at a pre-set time.
Altimeter: A device that determines altitude by responding to changes in barometric pressure.
Analog Display: A display that shows the time by means of hands and a dial.
Analog Watch: A watch with a dial, hands, and numbers or markers that present a total display of 12-hour time span. Analog digital refers to a watch that has both a digital display and hands of a conventional watch.
Aperture: Small opening. The dials of some watches (in French: montres à guichet) have apertures in which certain indications are given (e.g. the date, the hour, etc).
Automatic Movement: A mechanical movement that requires no winding because the rotor, part of the automatic mechanism, winds the mainspring every time you move your hand. The first automatic movement was invented in Switzerland by Abraham-Louis Perrelet in the Eighteenth century. When fully wound and left to sit, most automatics have up to 36 hours of reserve power. Mechanical movements are accurate within one minute each day. Automatic movements have gained in popularity the last few years especially with watch connoisseurs and are considered to be Switzerland's mechanical answer to the popularity of the no-winding-needed quartz movements that are standard in Japanese watches.
Auto Repeat Countdown Timer: A countdown timer that resets itself as soon as the preset time has elapsed and starts the countdown again. It repeats the countdown continuously until the wearer pushes the stop button.
Automatic Watch: A watch whose mainspring is wound by the movements or accelerations of the wearer's arm. On the basis of the principle of terrestrial attraction, a rotor turns and transmits its energy to the spring by means of an appropriate mechanism. The system was invented in Switzerland by Abraham-Louis Perrelet in the 18th century.
Automatic Winding: (also called "self-winding") Winding that occurs through the motion of the wearer's arm rather than through turning the winding stem. It works by means of a rotor that turns in response to motion, thereby winding up the watch's mainspring. An automatic watch that is not worn for a day or two will wind down and need to be wound by hand to get it started again.
Balance Spring: A very fine spring (also called a "hair spring") in a mechanical watch that returns the balance wheel back to a neutral position.
Balance Wheel: The part of a mechanical watch movement that oscillates, dividing time into equal segments.
Barrel: Thin cylindrical box containing the mainspring of a watch. The toothed rim of the barrel drives the train.
Bezel: The ring, usually made of gold, gold plate or steel, that surrounds the watch face.
Bi-directional Rotating Bezel: A bezel that can be moved either clockwise or counterclockwise. These are used for mathematical calculations or for keeping track of elapsed time.
Bracelet: A type of watch band made of elements that resemble links.
Bridge: Complementary part fixed to the main plate to form the frame of a watch movement. The other parts are mounted inside the frame.
Calendar: A feature that shows the day of the month, and often the day of the week and the year. There are several types of calendar watches.
Caliber: A term often used by Swiss watchmakers to denote a particular model type, such as Caliber 48 meaning model 48. More commonly, the term is used to indicate the movement's shape, layout, or size.
Cambered: Often used in referring to a curved or arched dial or bezel.
Case: The metal housing of a watch's parts. Stainless steel is the most typical metal used but titanium, gold, silver, and platinum can also be used. Less expensive watches are usually made of brass and plated with gold or silver.
Caseback: The reverse side of a watch case that lies against the skin. May be transparent to allow viewing of the inner workings of the watch or be solid. Most manufacturers engrave casebacks with their name, water and shock resistance, case metal content and other details.
Chime: The bell-like sound made when a clock strikes on the hour, half hour, etc. Two familiar chimes traditionally found in clocks are the Westminster chime made by the famous Big Ben in London, and the bim bam, a two note chime.
Chronograph: A stopwatch, i.e., a timer that can be started and stopped to time an event. There are many variations on the chronograph. Some operate with a center seconds hand which keeps time on the watch's main dial. Others use subdials to elapsed hours, minutes and seconds. Still others show elapsed time on a digital display on the watch face. When a chronograph is used in conjunction with specialized scales on the watch face, it can perform many different functions, such as determining speed or distance. Some chronographs can time more than one event at a time. Do not confuse the term "chronograph" with "chronometer". The latter refers to a timepiece, which may or may not have a chronograph function, that's met certain high standards of accuracy set by an official watch institute in Switzerland. Watches that include the chronograph function are themselves called "chronographs".
Chronometer: This term refers to a precision watch that is tested in various temperatures and positions, thus meeting the accuracy standards set by an official institute in Switzerland. Most watch companies provide a certificate with your chronometer purchase.
Complication: A watch with other functions besides timekeeping. For example, a chronograph is a watch complication. Other complications coveted by watch collectors include: minute repeater, tourbillon, perpetual calendar, or split second chronograph.
COSC: The official Swiss Chronometer Testing Institute that puts every chronometer watch through a rigorous, 15-day testing procedure to verify the watch's precision.
Countdown Timer: A function that lets the wearer keep track of how much of a pre-set period of time has elapsed. Some countdown timers sound a warning signal a few seconds before time runs out -- these are useful in events such as yacht races, where the sailor must maneuver the boat into position before the start of a race.
Crown: Button on the outside of the case that is used to set the time and the calendar, and, in the mechanical watches, to wind the mainspring.
Crystal: The transparent cover on the watch face made of glass crystal, synthetic sapphire or plastic.
Day/Date Watch: A watch that indicates not only the date but also the day of the week.
Day/Night Indicator: A colored or shaded band on a world time that shows which time zones are in daylight and which in darkness.
Depth Alarm: An alarm on a diver's watch that sounds when the wearer exceeds a pre-set depth. In most watches it stops sounding when the diver ascends above that depth.
Dial: The watch face. In high-end watches the numerals, indices and surface designs are applied as separate elements. In less expensive watches, they may be simply printed on the dial.
Digital watch: A watch that shows the time through digits rather than through a dial and hands display.
Direct-drive: A function that allows the second-hand to advance in intervals rather than a smooth sweep for more precise timekeeping. The French term for a direct-drive second hand is a trotteuse.
Dual Timer: A watch that measures current local time as well as at least one other time zone. The additional time element may come from a twin dial, extra hand, subdials, or other means.
Elapsed Time Rotating Bezel: A graduated rotating bezel used to keep track of periods of time. The bezel can be turned so the wearer can align the zero on the bezel with the watch's seconds or minutes hand. He/she can then read the elapsed time off the bezel. This saves him/her having to perform the subtraction that would be necessary if he used the watch's regular dial.
Engine turning: Decorative engraving, usually on the watch face.
Escapement: Device in a mechanical movement that controls the rotation of the wheels and thus the motion of the hands.
Face: The visible side of the watch where the dial is contained. Most faces are marked with Arabic or Roman numerals to indicate the hours. Interestingly, when Roman numerals are used, it is traditional to use IIII, rather than IV, to indicate the 4 o'clock position.
Flyback hand: A seconds hand on the chronograph that can be used to time laps or to determine finishing times for several competitors in race.
Gasket: Most water resistant watches are equipped with gaskets to seal the case back, crystal, and crown to protect against water infiltration during normal wear. It is important to have the gaskets checked every two years to maintain the water resistance of the watch.
Gear train: The system of gears which transmits power from the mainspring to the escapement.
Grande Sonnerie: A type of repeater that sounds the hours and quarter hours when the wearer pushes the button.
Guilloche: A style of intricate engraving that is popular on watch dials, usually very thin lines interwoven to create a surface texture.
Index: An hour indicator on an analog watch dial, used instead of numerals.
Jewels: Synthetic sapphires or rubies that acts as bearings for gears in the mechanical watch, reducing friction.
Jump Hour Indicator: A jump hour indicator takes the place of an hour hand. It usually shows the hours by means of a numeral in a window.
Lap Memory: The ability, in some quartz sport watches, to preserve in the watch's memory the times of laps in a race that have been determined by the lap timer. The wearer can recall these times on a digital display by pushing a button.
Lap Timer: A chronograph function that lets the wearer time segments of a race. At the end of a lap, he/she stops the timer, which then returns to zero to begin timing the next lap.
Liquid-Crystal Display: A digital watch display that shows the time electronically by means of the liquid held in a thin layer between two transparent plates.
Lugs: Projection on the watch face to which the watch band/bracelet is attached.
Main Plate: Base plate on which all the other parts of a watch movement are mounted.
Mainspring: The driving spring of a watch or clock, contained in the barrel.
Manual Wind: A manual wind watch must be wound every day by the crown in order to run. Even with that inconvenience, they are still produced by the major houses in Switzerland. Some of the most beautiful pieces made today are manual wind, and you actually won't fund many value or budget manual winds (but they exist!). With exhibition backs becoming very common, it's nice to view the active movement without a rotor in the way.
Marine Chronometer: Highly accurate mechanical or electronic timekeeper enclosed in a box (hence the term box chronometer), used for determining the longitude on board ship. Marine chronometers with mechanical movements are mounted on gimbals so that they remain in the horizontal position is necessary for their precision.
Measurement Conversion: A feature, usually consisting of a graduated scale on the watch's bezel, that lets the wearer translate one type of measurement into another -- miles into kilometers, for instance, or pounds into kilograms.
Mechanical Movement: A movement based on a mainspring which is wound by hand; when wound, it slowly unwinds the spring in an even motion. An automatic mechanical requires no winding because of the rotor, which winds the mainspring every time you move your wrist.
Military or 24-hour time: When time is measured in 24-hour segments. To convert 12-hour time into 24-hour, simple add 12 to any p.m. time. To convert 24-hour time into 12-hour time, subtract 12 from any time 13 to 24.
Moon-phase: A window in a watch face that shows which phase the moon is.
Mother-of-Pearl: Iridescent milky interior shell of the freshwater mollusk that is sliced thin and used on watch dials. While most have a milky white luster, mother-of-pearl also comes in other colors such as silvery gray, gray blue, pink and salmon.
Movement: The inner mechanism of watch that keeps time and moves the watch's hand, calendar, etc. Movements are either mechanical or quartz.
Perpetual Calendar: A calendar that automatically adjusts for the months' varying length and for leap year. Perpetual calendars, which can be powered by quartz or mechanical movements, are programmed to be accurate until the year 2100. Many watch collectors suggest storing mechanical versions in motorized winding boxes when they aren't being worn in order to maintain the calendar countdown.
Power Reserve: The amount of energy reserve stored up to keep a watch running until it stops. The remaining power is sometimes indicated by a small gauge on the dial.
Power Reserve Indicator: A feature of a mechanical watch that shows how much longer the watch will operate before it must be wound again.
Push-piece: Button that is pressed to work a mechanism. (The push-pieces on chronographs, striking watches, alarms, etc.)
Quartz Crystal: A tiny piece of synthetic quartz that oscillates at the rate of 32.768 times a second, dividing time into equal segments.
Quartz Movement: A movement which allows a watch to keep time without being wound. This technology employs the vibrations of a tiny crystal to maintain timing accuracy. The power comes from a battery that must be replaced about every 1.5 years. In recent years, new quartz technology enables the watch to recharge itself without battery replacement. This power is generated via body motion similar to an automatic mechanical watch, or powered by light through a solar cell, or even by body heat. A digital quartz watch has no mechanical parts. Most quartz movements are made in Hong Kong, Japan or Switzerland.
Repeater: A device that chimes the time when the wearer pushes a button.
Rotating Bezel: A bezel (the ring surrounding the watch face) that can be turned. Different types of rotating bezels perform different timekeeping and mathematical functions.
Rotor: The part of an automatic watch that winds the the movement's main spring.
Sapphire Crystal: A crystal (the cover that protects the watch face) made of synthetic sapphire, a transparent shatter-resistant, scratch-resistant substance.
Screw-Lock Crown: A crown that can be screwed into the case to make the watch watertight.
Second Time-Zone Indicator: An additional dial that can be set to the time in another time zone. It lets the wearer keep track of local time and the time in another country simultaneously.
Shock Absorber: Resilient bearing which, in a watch, is intended to take up the shocks received by the balance staff and thus protects its delicate pivots from damage.
Shock Resistance: As defined by the US Government regulation, a watch's ability to withstand an impact equal to that of being dropped onto wood floor from a height of 3 feet.
Skeleton Case: A case with a transparent front or back that allows the wearer to view the watch's movement.
Solar Compass: A compass that lets the wearer determine the geographical poles by means of a rotating bezel. The wearer places the watch so that the hour hand faces the sun. He then takes half the distance between the position and 12 o'clock, and turns the bezel until its "south" marker is at that halfway point. Some quartz watches have solar compasses that show directions on an LCD display.
Split Seconds Hand: Actually two hands, one a flyback hand the other a regular chronograph hand. When the wearer starts the chronograph, both hands move together. To time laps or different finishing times, the wearer can stop the flyback hand independently while the regular chronograph hand keeps moving, in effect "splitting" the hand(s) in two.
Stepping Motor: The part of a quartz movement that moves the gear train, which in turn moves the watch's hands.
Stopwatch: A watch with a seconds hand that measures intervals of time. When a stopwatch is incorporated into a standard watch, both the stopwatch function and the timepiece are referred to as a "chronograph". Subdial: A small dial on the watch face used for any of several purposes, such as keeping track of elapsed minutes or hours on the chronograph or indicating the date.
Swiss Made: A watch is considered Swiss if its movement was assembled, started, adjusted and controlled by the manufacturer in Switzerland.
Swiss A.O.S.C. (Certificate of Origin): A mark identifying a watch that is assembled in Switzerland with components of Swiss origin.
Sweep Seconds-Hand: A seconds-hand that is mounted in the center of the watch dial.
Tachymeter: A device on the chronograph watch that measure the speed at which the wearer has traveled over a measured distance.
Tank Watch: A rectangular watch designed by Louis Cartier. The bars along the sides of the watch were inspired by the tracks of tanks used in World War I.
Telemeter: A telemeter determines the distance of an object from the observer by measuring how long it takes sound to travel that distance. Like a tachymeter, it consists of a stopwatch, or chronograph, and a special scale, usually on the outermost edge of the watch face.
30-Minute Recorder (or register): A subdial on a chronograph that can time periods of up to 30 minutes.
Timer: Instrument used for registering intervals of time (durations, brief times), without any indication of the time of day.
Tonneau Watch: A watch shaped like a barrel, with two convex sides.
Totalizer: A mechanism that keeps track of elapsed time and display it, usually on a sub-dial.
Tourbillon: A device in a mechanical watch that eliminates timekeeping errors cause by the slight difference in the rates at which a watch runs in the horizontal and vertical positions. The tourbillon consist of round carriage, or cage, holding the escapement and the balance. It rotates continuously at the rate of once per minute.
Tritium: An isotope of hydrogen that is used to activate the luminous dots or indices on a watch dial. The radioactivity released in this process is too slight to pose a health risk.
Uni-directional Rotating Bezel: An elapsed time rotating bezel, often found on divers' watches, that moves only in a counterclockwise direction. It is designed to prevent a diver who has unwittingly knocked the bezel off its original position from overestimating his remaining air supply. Because the bezel moves in only one direction, the diver can error only on the side of safety when timing his dive. Many divers' watches are ratcheted, so that they lock into place for greater safety.
Vibration: Movement of a pendulum or other oscillating element, limited by two consecutive extreme positions. The balance of a mechanical watch generally makes five or six vibrations per second (i.e. 18,000 or 21,600 per hour), but that of a high-frequency watch may make seven, eight or even ten vibrations per second (i.e. 25,200, 28,800 or 36, 000 per hour).
Water Resistance: A water resistant watch can handle light moisture, such as a rain or sink splashes, but should not be worn swimming or diving. If the watch can be submerged in water, it must state at what depth it maintains water resistance, i.e. 50 meters or more on most sport watches. Below 200 meters, the watch may be used for skin diving and even scuba diving depending upon the indicated depths.
Winding: Operation consisting in tightening the mainspring of a watch. This can be done by hand (by means of the crown) or automatically (by means of a rotor, which is caused to swing by the movements of the wearer's arm).
Winding Stem: The button on the right side of the watch case used to wind the mainspring. Also called a "crown".
World Time Dial: A dial, usually on the outer edge of the watch face, that tells the time up to 24 time zones around the world. The time zones are represented by the names of cities printed on the bezel or dial. The wearer reads the hour in a particular time zone by looking at the scale next to the city that the hour hand is pointing to. The minutes are read as normal. Watches with this feature are called "world timers".
Yacht Timer: A countdown timer that sounds warning signals during the countdown to a boat race.