Watch glossary

Alarm
A function on a watch that will make a sound or vibration at a pre-set time
Altimeter
An altimeter measures altitude, or height above sea level. Recording ascent and descent, an altimeter watch is an important piece of equipment for climbers, walkers, mountaineers and, of course, aviators.
Anadigi display
A display that shows the time both by hour and minute hands (an analogue display) and by numbers (a digital display). This is also known as duo display.
Analogue
A watch that uses hands and a dial to tell the time.
Aperture
A small opening found in the diamonds of some watches in which certain indications are given, such as the hour and the date.
Auto repeat countdown timer
A countdown timer that resets itself as soon as the preset time has elapsed and starts again. The countdown is repeated continuously until the stop button is pushed.
Automatic watch
A watch with a mechanical movement that has an additional mechanism called an oscillating weight. As this weight moves (caused by movement of the wrist), the mainspring is wound. Invented by Abraham-Louis Perrelet in the 18th century.
Automatic winding
Winding that occurs through movement of the wearer's arm, rather than by turning the winder. A rotor turns in response to motion, winding up the watch's mainspring. An automatic watch that is not worn for a day or two will wind down and may need to be rewound by hand to get it started again. This is also known as self-winding.
Balance spring
A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulates the timekeeping. This is also known as the hairspring.
Balance wheel
The part of a mechanical watch movement that oscillates, dividing time into equal segments. This is the regulating mechanism that controls the watch's timekeeping accuracy.
Barrel
A drum that holds the mainspring in a mechanical watch. The toothed rim of the barrel drives the train.
Bezel
The ring on the outside of the watch case, around the dial, or the rim that holds the watch glass. It may have calibrated markings, especially on sports or divers watches.
Bi-directional rotating bezel
A bezel that can be moved clockwise or anti-clockwise. It is used for keeping track of elapsed time.
Bracelet
The metal strap that goes around the wearer's wrist. A watch bracelet is often made up of flexible, separate links that can be removed to adjust the bracelet's length.
Bridge
A part that is fixed to the main plate to form the frame of a watch movement. All other parts are mounted inside the frame.
Calendar
A function that indicates day of the month and sometimes day of the week and the year.
Cambered
This refers to an arched or curved dial or bezel.
Caliber
The model reference of the watch movement.
Case
The metal housing that contains a watch's parts. Stainless steel is most commonly used although titanium, platinum, gold and silver can also be found. Less expensive watches are often made of brass and plated with gold-coloured or silver-coloured metals.
Chronograph
A watch that tells the time and acts as a stopwatch. The timing element can be stopped and started without interfering with the ability to tell the time. There are many different types. Some have a centre seconds hand which keeps time on the watch's main dial. Some use smaller subsidiary dials or a digital display to show elapsed time. A chronograph used in conjunction with specialized scales on the watch face can determine speed and distance. Some can time more than one event at one time.
Chronometer
A watch that has been vigorously tested in various positions and temperatures to ensure that it meets high standards of accuracy demanded by the COSC, the official Swiss chronometer testing institute. To be called a chronometer, the mechanical movement must achieve an average rate of between -4/+6 seconds per day.
Complication
A watch function other than timekeeping. These include chronograph, perpetual calendar, tourbillon and minute repeater. A watch with any additional function is called a complicated watch.
Countdown timer
This allows the wearer to know how much of a pre-set time has passed. Some sound a warning a few seconds before the pre-set time has elapsed.
Crown
The grooved button on the outside of the case, used for setting the hands on a watch, and the day and date, where applicable. It is also used for winding the mainspring of a mechanical watch. The crown is also known as a winder or winding stem.
Crystal
This is the clear cover on the watch face (dial). It may be made of glass, plastic, mineral crystal or sapphire crystal (a scratch-resistant synthetic material). Its purpose is to protect the watch face.
Day/date
A watch that shows the day and the date.

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Day/night indicator
A coloured or shaded band on a world time that shows which time zones are in daylight and which are in night-time.
Deployment buckle
This refers to two curved strips of hinged metal on a watch with a strap that fastens the strap tightly to the wrist. It tends to be a feature of quality watches.
Deployment clasp
This is similar to a deployment buckle but refers to a fastening on a bracelet watch.
Digital display
A watch that shows the time in numbers, or digits, rather than hands and a dial. Liquid crystal display (LCD)is commonly used.
Dual timer
A watch that shows local time and the time in at least one other time zone.
Duo display
A display that shows the time both by hour and minute hands (an analogue display) and by numbers (a digital display). This is also known as anadigi display.
Dial
This is the face of the watch, showing the time.
Elapsed time rotating bezel
A graduated rotating bezel that is used to keep track of periods of time. The bezel can be rotated so the wearer can align the zero of the bezel with the watch's minutes or seconds hand. The elapsed time can then be read off the bezel, rather than the wearer having to perform a subtraction necessary if he used the watch's regular dial.
EOL
This is the end-of-life indication in quartz battery powered watches.
Engine turning
This is a centuries-old craft that, today, involves the use of antique machines to engrave delicate patterns on metal watch components, including cases, dials, bezels and movements. It is also known as guilloche.
Escapement
The device in a mechanical movement that controls the rotation wheels and therefore the hands.
Flyback hand
A seconds hand on some chronograph watches that can be used to time laps or determine the finishing times for several race competitors. It is also known as rattrapante.
Function
A term used to describe the various different tasks a watch can perform such as chronograph and countdown timer. These are also known as complications.
Gear train
The system of gears which transmits power from the mainspring of the watch to the escapement.
Gold plating
A layer of gold that is plated onto a base metal case or bracelet to enhance its looks. The thickness of the plating is measured in microns (1000th of a mm).
Grand complication
A watch with a grand complication has at least three functions, or complications, in addition to timekeeping.
Hairspring
A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulates the watch's timekeeping. It is also known as a balance spring.
Horology
The science of time measurement, encompassing the art of designing and constructing watches.
Index
An hour indicator on an analogue watch dial, used instead of numeral.

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Integral bracelet
A bracelet that is shaped and attached to the case of a watch in such a way that it appears to be part of the watch, with the lines of the case smoothly continuing into the bracelet.
Jewels
Synthetic gemstones that act as bearings for the gear trains, reducing friction and wear.
Lap timer
A function in a chronograph watch that allows the wearer to time segments of a race. At the end of a lap, the timer is stopped and then returns to zero to begin timing the next segment.
Liquid crystal display
Liquid crystal display (LCD) watches show a numeric display continuously by means of the liquid held in a thin layer between two transparent plates. The numbers are made up from seven segments that form the number 8 when all are activated. They are activated by an electronic impulse.
Lugs
The arms of the watch case that hold the strap or bracelet.
Main plate
The base plate upon which all other parts of a watch movement are mounted.
Mainspring
The coiled spring which provides the power to drive a mechanical watch movement.
Marine chronometer
A highly accurate mechanical or electronic timekeeper that is enclosed in a box and is used for determining the longitude on board a ship. Marine chronometers with mechanical movements are mounted on gimbals so they are in the horizontal position that is essential for their precision.
Measurement conversion
A feature that allows the wearer to convert one type of measurement into another. It usually consists of a graduated scale on the bezel or dial.
Mechanical movement
This is the traditional watch movement. A mechanical watch is driven by a slow release of power from a mainspring via a set of small cog wheels. The spring is wound up manually.
Micron
This is a thousandth of a millimeter and is a measurement used for the thickness of gold plating.

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Minute repeater
A function on a watch that sound the time in hours, quarters or minutes.
Moonphase
A window in a watch which indicates the phases of the moon through 29 ½ days. Some moonphase watches incorporate a correction for the extra 44 minutes per month.
Mother of pearl
The iridescent interior of a freshwater mollusc, that is often used to decorate watch dials. Its colours include milky white, blue and pink.
Movement
The motor of a watch that makes it keep time and perform functions.
Multi functional
A watch that can perform different functions, such as a stopwatch or a countdown time, whilst still giving the correct time.
Perpetual calendar
A watch that automatically takes into account variations in the length of the month and leap years, and alters the calendar accordingly.
Platinum
Platinum is one of the rarest and most durable of precious metals. It doesn't tarnish and has a radiant, beautiful white lustre. It is a popular choice for prestigious watches set with gemstones.
Power reserve indicator
A feature of some mechanical watches which indicates how much longer the watch will operate before it needs to be wound again. It is also known as the reserve de marche.
Pulsimeter
A scale on a chronograph which is used for measuring pulse rate.
Push-piece
A button that is pressed to work a watch function such as a chronograph and an alarm.
Quartz crystal
The slice of synthetic quartz crystal within a quartz movement watch. When an electric current is passed through the quartz it oscillates. It oscillates at the rate of 32.768 hertz, dividing time into equal segments and therefore regulating the time.
Quartz movement
This is an electronic watch movement with a quartz crystal that oscillates when a current is applied to it. The power to run the watch is normally provided by a battery or a capacitor. A quartz movement is generally more accurate than a mechanical movement.
Rattrapante
A seconds hand on some chronographs that can be used to time laps or determine the finishing times for several race competitors. Also known as a flyback hand.
Regulator
A regulator what shows hours and minutes on separate dials, or sub dials.

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Rotating bezel
A bezel around the watch that can be rotated. It has various timekeeping functions.
Rotor
This is the oscillating part of an automatic watch that winds the mainspring.
Sapphire crystal
A crystal, the cover that protects the watch face, made of synthetic sapphire - a transparent, scratch resistant substance.
Screw down crown
A crown which screws down into a threaded barrel to aid a watch's water resistancy.
Second time zone indicator
An additional dial that can be set to the time in another time zone. This allows the wearer to know the time in two zones simultaneously.
Shock absorber
A resilient bearing which takes up the shocks received by the watch's balance staff and protects its pivots from damage.
Shock resistance
A watch's ability to withstand an impact equal to that of being dropped onto wood floor from a height of three feet.
Skeleton case
A watch case with a transparent front or back, allowing visibility of the watch's movement.
Slide rule
A device consisting of a scale on the outer edge of a watch face which enables mathematical calculations.
Solar powered batteries
Batteries in a quartz watch that are recharged via solar panels on the watch face.
Splits seconds hand
This refers to two hands - a flyback (rattrapante) hand and a regular chronograph hand. Both hands move together but, to time laps or finishing times, the wearer can stop the flyback hand while the chronograph hand continues. This, in effect, splits the hand in two.
Stainless steel
A durable metal alloy that is almost rust resistant and rarely corrodes or discolours and, therefore, is highly suitable for watch case and bracelets. It is sometimes used on the case backs of watches made of other metals.
Stopwatch
A watch with a seconds hand that measures intervals of time. When a stopwatch is incorporated into a watch, both the stopwatch and the standard watch are called a chronograph.
Stepping motor
The part of a quartz analogue movement that moves the gear train and in turn moves the watch's hands.
Sterling silver
Sterling silver is a highly reflective precious metal, which is 92.5% pure and is often used in watches.
Subsidiary dial
A small dial on a watch face used for purposes such as indicating the date or keeping track of elapsed time.
Swiss-made
A can only be said to be Swiss-made if its movement was assembled, started, adjusted and controlled by the manufacturer in Switzerland.
Swiss A.O.S.C.
A certificate of origin - a mark that identifies that a watch has been assembled in Switzerland and has components of Swiss origin.

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Tachymeter
A set of markings on the outside of a watch which measures the wearer's speed over a known distance. This is used in conjunction with the seconds hand.
Thirty minute recorder
A subsidiary dial on a chronograph that can time periods of up to 30 minutes.
Timer
A device for registering intervals of time with out any indication of the time of day.
Titanium
A metal with a silvery appearance that is stronger and lighter than steel. Titanium is used increasingly in watchmaking, especially for sports and divers watches as it is resistant to salt water corrosion.
Tonneau
A tonneau watch is shaped like a barrel with two convex sides.
Totaliser
A mechanism that keeps track of and displays elasped time, often on s subsidiary dial.
Tourbillon
A tourbillon is found in mechanical watches and is a device that eliminates timekeeping errors caused by the small differences in the rates a watch runs in the vertical and horizontal positions. It consists of a round cage, holding the balance and escapement. It rotates continuously at the rate of one rotation per minute.
Uni-directional rotating bezel
A bezel that can be rotated in one direction only and is used to monitor elapsed time. A ratchet mechanism is often in place to prevent it rotating in the other direction. It is often found on divers watches to prevent the diver from running out of air by overestimating remaining air supply if the bezel is accidentally knocked off its position. The fact the bezel moves in one direction only means the diver can only underestimate remaining air supply.
Vibration
This refers to the movement of an oscillating element that is limited by two extreme positions. The balance of a mechanical watch usually vibrates at a rate of five or six a second.
Water resistance
The ability of a watch to withstand water to various pressures.
Winding
This is the action of tightening the mainspring of a watch. It can be done manually, by means of the crown, or automatically, via a rotor which is made to swing by the movement of the wearer's wrist.
Winding stem
The grooved button on the outside of the case, used for setting the hands on a watch, and the day and date where applicable. It is also used for winding the mainspring of a mechanical watch. It is also known as the crown.
World time dial
A dial that tells the time of up to 24 time zones around the world. The names of the cities are printed on the dial. The hour in a particular zone can be read by looking at the scale next to the city that the hour hand is pointing to. The minutes are read in the normal way. The dial is usually found on the outer edge of the watch face. Watches with this function are called world timers.
Yacht timer
A countdown time which shows or sounds warning signals during the countdown to a boat race.

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