A-Z

Watch Terms

A

• Acrylic

A plastic used to make crystals. It's very soft, but is easy to repair and does not shatter when it breaks. Watches designed for use in space have acrylic crystals.

• Analog

A display of time or other data using dials and hands, as opposed to a digital readout. After a hiatus in the 1980s, the format has become increasingly popular.

• Analog-digital display

A watch display that combines analogue and digital elements, usually found on Quartz watches, though there are some mechanical versions

• Anti-magnetic

A type of mechanical watch movement that is designed to be highly resistant to magnetic fields that could adversely affect or stop it.

• Automatic winder

A box or cabinet with motorized rotating slots to hold watches with automatic movements. The rotation keeps the watch wound by spinning the movement's rotor, and accurate by counteracting the effects of gravity. Some winders are incorporated into special safes to hold collector automatic watches that cost six figures.

• Automatic winding

Also called self-winding or simply automatic. A mechanical watch movement that is wound by the motions of the wearer by either spinning a rotor or oscillating a weight. Failure to wear the watch regularly will cause it to stop once its power reserve is exhausted.

B

• Balance

The oscillator on a mechanical watch that regulates the movement so it runs in a series of beats or vibrations.

• Balance spring

See Hairspring.

• Balance wheel

An oscillating wheel that regulates the movement by dividing time into regular beats

• Balance cock

A bridge with a lug anchored to a stud. It holds the top pivot of the watch's balance staff.

• Bezel

A ring around the watch face made of stainless steel, ceramic, precious metal or base metal. It can be either decorative or movable. If the latter, it may be inside or outside the crystal and rotate to act as a timer, tachymeter, slide rule, or other function.

• Bi-color

See Two-tone

• Bi-directional rotating bezel

A bezel that can rotate either clockwise or anticlockwise to perform a function.

• Bracelet

A watch band made of movable links. These can be adjusted to fit the wearer and may have special clasps that allow them to expand to fit over a wetsuit or jacket.

• Bridge

A plate or bar set on a movement's main plate to act as a frame to hold a watch's inner workings. They can also be shaped or decorated in skeleton watches for aesthetic purposes.

C

• Calendar

A complication that shows the date and may also show the day of the week, the month, or even the year. Some calendar watches need to be adjusted manually whenever the month is less than 31 days long. Others, called perpetual calendars, are self-adjusting over several decades or centuries.

• Caliber

See Movement.

• Cambered

An arched or curved bezel or dial.

• Case

The housing used to protect the movement. Usually made of base or precious metal, it can also be made of plastic, carbon composite, ceramic, rubber, or other materials.

• Case back

The back or reverse of a watch designed to protect the movement. These are generally made of stainless steel, though they may include a crystal to show off the workings inside. Case backs may be simply snapped in place or screwed in with rubber gaskets to protect against water and dust. These often include information about the watch, like hallmarks, major specifications, or a serial number.

• Chapter ring

A ring of symbols or marks on a watch dial to indicate minutes or seconds.

• Chapters

Large marks on a chapter ring to denote hours. Quarter hours often have their own chapters.

• Chronograph

A complication that allows a watch to act as a stopwatch with a precision of down to a tenth or a hundredth of a second. Some versions allow lap timing as well for individual contestants in a race or events in a process.

• Chronometer

A precision timepiece capable of keeping time with a precision and accuracy suitable for navigation. Swiss-made watches are certified as chronometers by meeting the standards set by the Swiss Official Chronometer Control (COSC), which includes several days of rigorous testing under various pressures and temperatures.

• Clasp

Fastening mechanism for straps and bracelets. Leather, rubber, and cloth bands tend to use buckles, though bracelets and expensive leather straps use deployment straps for a tighter fit with less wear.

• Complication

Any function on a watch beyond displaying hours, minutes, and seconds. These can include even unseen things like an automatic winding function.

• Cosmograph

A chronometer developed and named by Rolex that has a tachymeter mounted on the bezel instead of the dial.

• Countdown timer

A complication that counts down in reverse from a preset time, like for timing an egg or a parking meter. This can include an alarm to alert the wearer when the time has elapsed, though that is usually found on quartz watches.

• Counterfeit watch

An illegal copy of a watch that is passed off by the maker as the real thing.

• Crown

A button on the side of the case that pulls or screws out, allowing the wearer to adjust the time and date or synchronize the seconds. In non-automatic watches, it is also used to wind the mainspring. Screw-in or screw-down crowns, or similar mechanisms, seal the watch to keep out water at extreme depths.

• Crystal

A transparent cover over the dial or in the case back, or it may make up the entire case. It can be made of ordinary glass, mineral glass, acrylic plastic, synthetic sapphire, or ruby. Sapphire is preferred for high-end watches because it's almost as hard as diamond, though many use plastic because it's easy to repair and cracks instead of shattering into small, potentially dangerous fragments.

• Cyclops

A small blister on a crystal that acts a magnifying lens to make the date more legible.

D

• Day/date watch

A watch with indicators or windows to display both the date and the day of the week. These require a more complicated mechanism to allow them to be adjusted quickly without jamming.

• Day/night indicator

A colored indicator on a dual or world time watch that shows if the home and second time zones are in daylight or night. It's particularly useful for watches without a 24-hour readout.

• Deployment clasp

A buckle that allows a strap or bracelet to stay in one piece, by opening and fastening using a hinged plate with adjustable extenders. The latter are particularly popular with divers or aviators, who may need to adjust the band to go over a wetsuit or jacket.

• Dial

The face of the watch, which carries the hands, marks, indicators, and subdials. A dial may be plain, highly ornate, or divided into bridges to make the movement visible.

• Digital watch

A watch that shows the time and other information through a digital display instead of with hands. Digital watches are associated with quartz watches first marketed in the 1970s, which used LED and LCD displays, but mechanical digital watches date back to the 19th century and have appeared from time to time as novelty items. It was widely believed in the 1970s and 80s that digital watches would not only drive out analog ones, but analog timekeeping as well. However, recent decades have seen a resurgence of analog watches with digitals withdrawing to the cheapest or most specialized markets.

• Dive watch

Also called a diver or diver's watch. A watch with a case designed to remain water resistant to depths of at least 200 m (660 ft). It also includes a dial designed to be legible at a glance under poor light conditions, and may have an elapsed time bezel for timing decompression stops. These have been superseded by wrist dive computers, but most divers still wear a dive watch as a back-up.

• Doctor's watch

A watch that is robust, easy to keep clean and sterile, and has a special seconds hand and markings to allow a doctor to quickly measure a patient's pulse.

• Dolphin standard

A water-resistant watch that is suitable for swimming, snorkelling, boating and other water sports.

• Dual time

A watch that is able to display the time in two separate time zones simultaneously.

E

• Elapsed-time bezel

A rotating bezel for tracking elapsed time by lining up the zero mark with the minute hand, so the result can be read directly.

• Electric or electronic watch

A watch that runs on electric current instead of a mechanical movement. This generally refers to a quartz movement, but can also be used in regard to watches using tuning forks or other electric or electronic regulators.

• EOL

End Of Life. This is an indicator on quartz watches that shows that the battery is almost exhausted and needs replacing.

• Equation of time

A complication that shows the difference between true solar time and mean solar time. The Equation of time complication shows by how much the two times diverge from one another on a particular day.

• Escapement

The part of the watch movement that divides the time into a series of beats or oscillations.

F

• Face

See Dial.

• Field watch

A watch originally designed to be issued to soldiers for use on the battlefield. They are notable by their simple, rugged, and easy to service construction.

• Flyback

A hand on watches and especially chronographs that immediately jumps back to zero. On a regular watch, it can be used to conserve space on the dial by having a minute or second hand travel along an arc instead of revolving around the whole dial. When it reaches the end, it jumps back to zero in an instant. On chronographs, the flyback hand is used to record elapsed time, and restarts the instant it is reset to zero without the need to stop and start the watch again. It's particularly useful when repeatedly timing a series of events.

• Frequency

A measurement of a watch movement's speed as measured in the number of semi-oscillations or half-turns of the balance spring. These are measured in beats or vibrations per hour (bph, vph) or Hertz. The higher the frequency, the smoother and more accurate the movement – which is especially useful in chronographs that measure in hundredths of a second. A modern wrist watch usually has a frequency of 4 Hz (28,800 vph).

• Function

A general term for the things that a watch can do. The term is different than a complication because functions can include basic timekeeping.

• Fusee

An obsolete way of equalizing the power of a mainspring as a watch unwinds by using a chain wound around a spiral-grooved, truncated cone. As the watch winds down, the chain is unwrapped from the narrow top of the cone and onto the mainspring barrel. Because the mainspring has less force as it unwinds, the chain sitting in progressively wider grooves of the spiral compensates and the watch runs properly.

G

• Gasket

A rubber ring set in a watch case back, crown, or crystal to protect against water and dust. Improper replacement while servicing can ruin your whole day.

• Gear train

The series of gears of a watch movement that runs between the mainspring and the display or a complication. The arrangement controls the running of the watch.

• Geneva seal

Also called the "Poinçon de Genève." The official seal of the City and Canton of Geneva, Switzerland. In horology, it's used as a quality seal by the Watchmaking School of Geneva on watches made in the Canton that have been submitted for and passed a special inspection. This is based on 12 criteria regarding the movement's materials and finishing.

• Geneva waves

Also called "Geneva stripes" or "côtes de Genève." These are decorations consisting of stripes applied to a watch's plates, bridges, balance cocks or rotors.

• GMT

Greenwich Mean Time (GMT) is the time at the Prime or Zero Meridian that runs through the Royal Observatory at Greenwich, England and is not subject to summer time or daylight savings time. It's often confused with Coordinated Universal Time (UTC), but the latter is actually a precisely determined scientific time standard, which is constantly adjusted to remain in step with time as it is marked by an atomic clock.

• GMT watch

A watch with a second hour hand that is set to mark the time at Greenwich. In conjunction with a special 24-hour bezel, it allows the wearer to quickly read the time in different zones. Alternatively, the additional hand can be set to any desired second time zone.

• Gold plating

A way of giving a watch case or bracelet the look of gold by electroplating it with a layer of the precious metal. Since the thickness of such plating is only a few microns, the finish is subject to wear in daily use. For this reason, many watches are available in two-tone finishes to preserve the gold by restricting it to less vulnerable areas of the watch.

• Grail watch

A highly valued watch – usually one that's out of the price range of the person who desires it.

• Grande complications

A mechanical watch that includes a large number of functions or complications. Such watches are not meant for practical use, but as showcases for craftsmanship.

• Grande sonnerie

A watch or other timepiece that chimes at the hour, half hour, and quarter-hours automatically or when the wearer presses a button. The mechanism often includes different chimes of different pitches to allow the wearer to determine the time within the quarter-hour by hearing alone. Very elaborate versions may even include an automaton like a small singing bird.

• Guilloche

Also called Engine Turning. This is a very precise engraving technique designed to produce intricate, repetitive designs on a material, including those used on dials.

H

• Hairspring

Also called a balance spring. The very fine metallic spring in a watch movement that allows the balance wheel to recoil. Its length can be adjusted to regulate the watch by making it run faster or slower.

• Hacking seconds

Also called hack seconds or stop seconds. A hacking seconds function allows the wearer to stop the seconds hand, usually by pulling out the crown to a preset stop, while the rest of the mechanism continues to run and keeps the time. It's used to synchronize the watch with someone else's or with a reference time signal without having to adjust the time.

• Hallmark

A form of consumer protection going back 700 years. These are marks stamped on a watch case by a company or some official body that conveys information. They can guarantee the purity of a precious metal used in the case, the quality of the watch as determined by independent inspectors, the country or city of origin, water resistance, serial numbers, manufacturer, year of manufacture, caliber reference, or trademark.

• Hand-wound movement

Also called a manual-wind movement. A mechanical movement that requires periodic winding by hand to function. These often include mechanisms to prevent overwinding.

• Hands

The part of the watch display used to convey information. The hands can come in many forms for aesthetic or practical reasons. In tool watches, it is common for the hands to be shaped as to be difficult to mistake for one another.

• Haute chronologie

Upmarket watchmaking. The term is a play on the fashion industry's haute couture.

• Hard metal

A metal casing made by cementing together titanium and tungsten carbide particles in a high-pressure press. The result is an extremely hard, scratch-resistant material that can be polished with diamond powder. However, it is also very brittle and cannot be repaired if damaged.

• Helium escape valve

Also called a helium release valve. A valve set in a dive watch to prevent it from being damaged by helium. Dive watches with water resistance ratings of over 300 m (1,000 ft) are often worn by mixed-gas divers, who breathe a mixture of helium, hydrogen, and oxygen when working at extreme depths. In between dives and when returning to the surface, the divers sit in a compression chamber filled with the same gas mixture. Because helium molecules are so tiny, they can slip past the watch's gasket and into the case. When the divers leave the chamber and return to sea level pressure, this trapped gas could severely damage the watch, so the one-way helium release valve is used to bleed off the helium when the internal case pressure becomes too great.

• Hertz

Unit for measuring frequencies in cycles per second. It's abbreviated as "Hz."

• Hesalite

A kind of acrylic crystal as used on the Omega Speedmaster Professional and many others.

• Homage watch

A watch that deliberately mimics the design cues of a classic and far more expensive watch without pretending to be that watch, as opposed to a counterfeit or, "replica."

• Horology

The study of time measurement, sundials, clocks, chronometers, watches, and other timepieces, and their construction.

• Hybrid watch

A watch that combines mechanical and smartwatch components.

I

• Illumination

A device that lights up the display on the watch on command. This can include simple electric lights; LEDs; photoluminescent materials like Super-LumiNova, LumiNova, or LumiBrite that absorb and re-emit light; phosphorescent materials embedded with radioactive isotopes like radium; and tritium-filled tubes called trasers among others.

• Incabloc

A brand of shock absorber for mechanical watches designed to protect a movement's watch balance staff.

• Index

A simple mark on a watch dial designed to indicate the hours.

• Integrated bracelet

A watch strap or bracelet that blends into the case and is not detachable. It's most commonly found on fashion watches with a plastic or silicone rubber case and strap.

J

• Jewels

Sapphires or rubies (usually synthetic) that are shaped into gear bearings to reduce friction and increase the life of the movement between servicing.

• Jump hours/minutes

Instead of using analog hands and marks on a dial, jump hours or minutes are a way of producing a digital display using a mechanical movement. In a jumping display, numbered discs rotate behind the watch face and are made visible through an aperture. It's called a jumping display because, where hands move gradually from one mark to the next, the numbers in the aperture remain static until the next minute or hour arrives, then jump ahead.

• Jump seconds

Also called deadbeat seconds, this is a way to make mechanical watch movements shift the seconds hand in discrete one-second intervals in a single tick like a quartz movement. Pendulum clocks have used deadbeat seconds since 1675, but modern mechanical movements usually tick five to ten times per second. Some haute chronologie watches can be made to display deadbeat, though the reason for doing this is simply to show off the complex mechanism needed to achieve it.

K

• Karat

The standard for showing the purity of precious metals indicated by the abbreviation "k." 24k gold is pure, but 18k gold is 75 percent pure. The addition of other metals to gold is required because pure gold is too soft to be practical.

• Keeper

Loops on a watch strap or band designed to keep the surplus end length of the strap in place after its been fastened. ALSO, a watch in a collection that one is reluctant to sell as it is worn regularly and becomes 'a keeper'.

• Kinetic

A technology developed by Seiko for its superquartz movements. Its purpose is to change the wearer's movements into electricity to keep the watch battery fully charged.

L

• Lap timer

A chronograph or stopwatch function that can record the time for individual events in a race, including a runner's laps. When each lap is counted, it returns to zero to time the next lap.

• Lever escapement

Also called an anchor escapement. An escapement that uses an anchor-shaped lever with two pallets to lock and unlock the escapement wheel's teeth.

• Limited edition

A watch that is manufactured and sold in a finite number of units that are often numbered. The purpose is to increase their value.

• Liquid crystal display (LCD)

A flat display on a digital watch that uses liquid crystals sealed in a layer between two transparent plates in a series of sections. When an electric current is applied to a section, its optical properties change and it becomes opaque. This allows it to display digits, letters, and symbols depending on the display's design.

• Lug

Curved protrusions from a wristwatch case for the attachment of a strap or bracelet by means of spring-loaded pins. The inside measurement will determine the size of the strap or bracelet.

• Luminescence

See Illumination.

• Light emitting diode (LED)

A display that uses diodes that emit light when energized. These were used in the first digital watches but were so energy-hungry that they could only be illuminated for a fraction of a second by pressing a button, with the display being invisible the rest of the time.

• Ligne

A historic French unit of measurement used in watchmaking, equivalent to 2.2558291 mm.

M

• 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.

• 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. Omega Marine Chronometer

• 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 powered by a mainspring, working in conjunction with a balance wheel. Most watches today have electronically controlled quartz movements and are powered by a battery. However, mechanical watches are currently enjoying a resurgence in popularity.

• Movement

The inner mechanism of a watch that keeps time and moves the watch's hands, calendar, etc. Movements are either mechanical or quartz.