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Watch Glossary--Amazon.co.uk's Guide to Watch Terms

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A device that makes an alerting sound at a preset time. Alarm watches can be either quartz or mechanical.


A function, commonly found in pilot watches or inside a pressurized airplane cabin, that shows altitude by responding to changes in barometric pressure.

Analog Watch:

A watch that has a dial, hands, numbers, or other types of markers that present a total display of 12 hours.

Analog-Digital Display Watch:

A watch that shows the time by means of hands (analog display) as well as numbers (digital display). This is most often found in sport watches. The analog display has a traditional dial with hour, minute, and sometimes seconds hands. The digital display shows the time in Arabic numerals with a liquid crystal display.

Annual Calendar Watch:

A watch showing the day, date, month, and 24 hours, adjusting automatically for short and long months. The calendar needs setting only once a year between the end of February and the first of March.


Small openings carved into the watch that display certain indications, such as the date or hour. Some apertures may only be visible when the watch dials are in certain positions.

Atmosphere (ATM):

Measures the normal pressure of the air at sea level. It is used in watchmaking to indicate water-resistance. ATM is short for atmosphere and is roughly the equivalent of ten metres in depth, i.e., a watch with a rating of 1 ATM is safe under ten metres of water, 5 ATM rating means 50 metres.

Automatic Movement (Automatic Winding, or Self-Winding):

A watch mechanically powered by the motion of the wearer's arm rather than by manually turning the winding stem. In response to this motion, a rotor turns and winds the watch's mainspring so that it keeps accurate time. Most automatic watches have up to 36 hours of power reserve. If an automatic watch is not worn for a day or two, it will need to be wound by hand to restart again.

Band Width:

Measures the distance between the case lugs (the point that the strap is fixed to the watch case). Therefore, band width may not necessarily be the exact width of the watch band, as a bracelet or strap can have tapering widths. When swapping watch bands or purchasing replacement bands, the band width of the new band must match the distance between the case lugs.


Generically, the upper part of the watch body. Specifically, it usually refers to a ring that goes around the outside of the crystal. On jewellery-style watches, for instance, the bezel may contain a ring of diamonds. On sports watches, the bezel may show calibrated markings and have the ability to rotate in one or two directions.

Bi-directional Rotating Bezel:

A bezel that can be moved either clockwise or counterclockwise, usually used for mathematical calculations or keeping track of elapsed time.


The acronym for the Contrôle Officiel Suisse des Chronomètres (the Official Swiss Chronometer Testing Institute), the institute responsible for certifying the accuracy and precision of wrist watches in the country of Switzerland. A C.O.S.C. certified timepiece can be identified by a serial number that is engraved in the movement, and an additional certification number provided by the institute. To become certified as chronometer a watch must pass stringent internationally agreed tests relating to accuracy.

Case (Watch Case):

Refers to the metal housing that contains the internal parts of a watch. Most cases are made up of stainless steel, but titanium, gold, silver, and platinum are also used.

Case Diameter:

An approximate watch measurement from one end of the watch to the other that does not include the crown.

Case Thickness:

The thickness of the watch, measured from the highest point of the crystal to the base of the watch case.


A multifunction watch with a stopwatch function. These watches have two independent time systems. One tells the time of day while the other functions like a stopwatch. Most have two or three sub-dials or mini-dials for measuring intervals of time in minutes and hours. Most modern version have two pushers: One starts and stops the timing while the other resets the hands to zero when timing has stopped.


This term refers to a precision watch that is tested in various temperatures and positions, thus meeting the accuracy standards set by C.O.S.C. in Switzerland. These watches are provided with a chronometer certificate detailing specific test results.


Basic watches simply tell the time. Additional features beyond the simple display of hours, minutes, and seconds on a wrist watch are known as complications. However, features such as day-date displays, automatic movements, and chronographs do not necessarily label a watch as complicated. A watch that is complicated usually consists of more parts and, quite possibly, greater than a thousand parts. As a result, wrist watches with complications have a greater number of functions.


Often referred to as the winding crown or winder, a knob used for winding a manual watch, setting the hands to the correct time, and setting the date in calendar-equipped watches. On diving or sport models, the crown may screw down onto a threaded tube, which protrudes from the watch case to better ensure superior water-resistance.


The covering of the watch dial. Acrylic, mineral, and sapphire are three types of crystals commonly used in watches.

Acrylic crystal, sometimes referred to as Hesolite, is a plastic that is generally less expensive and less durable than a sapphire or a mineral crystal. Its flexible, malleable make-up means it will not shatter on impact, produces fewer glares under bright lights and allows shallow scratches to be buffed out. Mineral crystal is composed of several elements that are heat-treated to create an unusual hardness that helps resist scratches. Sapphire is the most expensive and durable crystal, approximately three times harder than mineral crystals and 20 times harder than acrylic crystals.

Daily Alarm:

Sounds each day at preset time.


A type of display that first appeared in the 1970s on wrist watches. Since then, digital watch technology has vastly improved, and continues to add on new and helpful features. In general, functions in digital watches work by push-buttons, either on the side of the watch case, or on the surface of the watch itself. Many kids' watches, as well as sports watches, feature digital-displays.

Diver's Watch:

Divers' watches traditionally feature a graduated rotating bezel, a screw-down winding crown, and a caseback; such watches must be water resistant to at least 200 metres (660 feet).

Dual Time:

The term dual time refers to 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, sub dial, or other means.

Elapsed Time:

Elapsed time refers to the actual amount of time it takes for an object to travel over a specified distance.

Elapsed Time Rotating Bezel:

A graduated rotating bezel (see "rotating bezel") is used to keep track of designated periods of time. The bezel can be turned so the wearer can align the zero with the watch's seconds or minutes hand. The wearer can then read the elapsed time off the bezel instead of having to calculate the elapsed time.

Exhibition Caseback:

Usually found in higher priced automatic or mechanical hand wind watches, an exhibition caseback provides a clear view of the intricate movements and parts of the inside of a watch. Rather than metal sitting on your wrist, a mineral or sapphire crystal replaces the base of the watch and allows for easy viewing.

Flyback Hand:

A flyback hand is an additional hand on a chronograph watch that moves with the seconds hand, but can be stopped independently to measure a preset interval of time. It can then "fly back" to catch up with the seconds hand. This feature is useful for capturing lap times as well as finish times.

GMT Time zone:

Greenwich Mean Time (GMT) is set to the international clock in Greenwich, England. Through an additional hour hand, a watch can reflect the world time on a 24-hour scale and is often used by pilots across the globe.

Hand winding (Manual Mechanical):

In order to keep accurate time a hand winding watch, with a manual mechanical movement, needs to be wound regularly by the wearer. This style of mechanical watch is wound using the winding crown. This motion winds the mainspring, which then releases its energy to power the watch.

Ionic Plating:

A physical vapor deposition (PVD) process that is often applied to stainless steel watch cases and bracelets, allowing a break from the traditional silver-tone stainless steel color, by coating a darker, dark-grey to black compound to the surface of the steel. This process is used to deposit hard coatings of compound materials in wrist watches.


Referring to the Seiko line of Kinetic watches, this technology has a Quartz movement that does not use a battery. Movement of the wearer’s wrist charges a very efficient capacitor that powers the Quartz movement.

Lap Memory:

Some Quartz sport watches are built with a lap memory which enables the watch to store the times of laps in a race determined by the lap timer (see "lap timer"). The wearer can recall these times on a digital display by pushing a button. Allow you to store lap/split times into memory. With a watch with 10 lap memories, 10 are stored. If more than 10, the first 9 and last are stored.

Lap Timer:

A lap timer is a chronograph function that lets the wearer time segments of a race. At the end of a lap, the wearer stops the timer, which then returns to zero in order to begin timing the next lap.


The extensions on the top and bottom of a wrist watch, where the bracelet, strap or band is attached to the watch dial. Band width measurements on all wrist watches are measured between the lugs.

LCD Display (Liquid Crystal Display):

An LCD display shows the time electronically by means of a liquid held in a thin layer between two transparent plates.

Manual Winding:

Manual winding refers to a watch with a manual mechanical movement, which needs to be wound by the winding crown. This motion winds the mainspring up which then releases its energy to power the watch.

Mechanical Movement:

A watch’s mechanical movement is based on a mainspring which slowly unwinds in a steady motion to provide accurate timekeeping. A manual mechanical watch needs to be wound on a consistent basis, while an automatic mechanical watch requires no winding because its rotor winds the mainspring when the wearer moves their wrist.

Military or 24 Hour Time:

When time is measured in 24-hour segments it is called military time. To convert 12-hour time to 24-hour time, simply add 12 to any p.m. time. To convert 24-hour time to 12-hour time, subtract 12 from 13 to 24.

Mineral Crystal:

Mineral crystal is made from what is essentially a form of glass. More scratch resistant than acrylic, a mineral crystal will, however, scratch and is difficult to polish.

Moon Phase:

The moon phase is an indicator that keeps track of the phases of the moon. A regular rotation of the moon is once around the earth every 29 days, 12 hours, and 44 minutes. Once set, the moon phase indicator accurately displays the phase of the moon.


Movement refers to the means by which a watch keeps time and often includes the power source. For example, a watch with mechanical movement uses a spinning balance wheel powered by a tightly wound spring. A watch with Quartz movement measures the vibrations in a piece of Quartz and often is powered by a battery.

Perpetual Calendar:

A perpetual calendar adjusts automatically to account for different lengths of months (30 or 31 days) and leap years. Perpetual calendars, which can be powered by Quartz or mechanical movements, are usually programmed to be accurate until the year 2100.

Power Reserve Indicator:

A power reserve indicator is a feature that shows when the watch will need a new battery or winding. A battery reserve indicator on a Quartz watch informs the wearer when the battery is low. Often this is indicated by the second’s hand moving at two- or three-second intervals.

Power Reserve:

A power reserve measures the amount of time a watch will run after being fully powered or wound, with no additional power input. Normally, a mechanical watch that is fully wound or a Quartz watch with a new battery has a full power reserve. Many modern mechanical watches have a power reserve of 40 hours. Power reserve also applies to battery-less Quartz watches, which may have power reserves from 40 hours to 6 months. On battery-operated Quartz watches, the term power reserve is sometimes used to refer to the expected battery life which is typically from 1 to 3 years.


A Quartz is a caliber that uses the vibrations of a tiny crystal to maintain timing accuracy. The power comes from a battery that must be replaced typically every 1 to 3 years. In recent years, new Quartz technology enables the watch to recharge itself without battery replacement. This power is generated via movement similar to an automatic mechanical watch, or powered by light through a solar cell (Kinetic & solar-tech).

Rattrapante Chronograph:

The addition of a fly back hand (rattrapante) significantly increases the potential uses for chronographs. It makes possible the measurement of split-second times or timing simultaneous events of unequal duration.


The register is another name for a sub dial that is usually found within the watch’s main dial. An example is a chronograph where there are registers for the chronograph minutes and hours. Some watches have registers with pointers showing the day and date.


A repeater is a device that chimes the time when the wearer pushes a button. Some repeaters, called "quarter repeaters" sound the hours and the quarter hours by means of two different pitched tones. Others called "five minute repeaters" sound the hours, quarters, and five minute periods while "minute repeaters" sound the hours, quarters, and minutes.


Retrograde is used to describe a pointer-hand on a watch dial (often called a sub dial), which returns to zero at the end of a set period. For example, a watch may have retrograde date where the hand moves up a scale, pointing to the current date - when it reaches 31 it will spring back to 1.

Rhodium Plated:

Rhodium plated is the protective coating of metal with a thin layer of rhodium. It is a hard, brittle metal that does not oxidize and is malleable only when red hot.

Rotating Bezel:

A rotating bezel (the ring surrounding the watch dial) that can be turned in order to perform different timekeeping and mathematical functions.


A rotor is the part of an automatic (or self-winding) mechanical watch that uses movement to wind the mainspring. It is a flat piece of metal, usually shaped like a semicircle, which swivels on a pivot with the motion of the wearer's arm.

Sapphire Crystal:

Synthetically formed, the sapphire crystal of a watch is extremely scratch resistant and is the material of choice for many watch collectors. The downsides are that the sapphire can chip at the edges if it protrudes and it can shatter.

Screw-Down Crown:

A screw-down crown aids water-resistance by sealing the crown to the case of the watch. A seal is achieved when the case locks with the crown's internal threads and gaskets fastening the crown into its place.

Second Time Zone Indicator:

The second time zone indicator is an additional dial that can be set to another time zone. It lets the wearer keep track of local time and the time in another country simultaneously.


Self-winding refers to a mechanically powered watch that is wound by the motion of the wearer's arm rather than by turning the winding stem (manual mechanical). In response to this motion, a rotor turns and winds the watch's mainspring. Most automatic watches have up to 40 hours of power reserve. If an automatic watch is not worn for a day or two, it will need to be wound by hand to get started again.

Shock Resistance:

Shock resistance is a watch's ability to withstand an impact equal to that of being dropped onto a wooden floor from a height of three feet.

Skeleton Caseback:

A caseback made of transparent material, such as hardened mineral or sapphire crystal, that reveals the intricate mechanical movements of the watch.

Solar Powered:

Solar powered refers to a type of Quartz movement where the batteries are recharged via solar panels on the watch dial. They have a power reserve so they can run in the dark.

Split Second:

A split second is a feature on a chronograph that is two hands: one is a fly back and the other is a regular hand. In order to time laps or different finishing times, the wearer can stop the fly back hand independently while the regular hand keeps moving.

Stainless Steel:

Stainless steel is an extremely durable metal alloy (chromium is a main ingredient) that is virtually immune to rust, discoloration, and corrosion. It can be highly polished, thus resembling a precious metal. Stainless steel is often used on the backs of watchcases that are made of other metals. A metal of choice, stainless steel is used to make high quality watchcases and bracelets. It is also hypoallergenic because it doesn't contain nickel.

Sterling Silver:

Sterling silver, a precious metal, refers to silver that is 92.5 percent pure. The silver fineness should be stamped on the metal, sometimes accompanied by the initials of a designer or the country of origin as a hallmark. A protective coating may be added to prevent tarnishing.


A stopwatch with a second hand 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."

Sub dial:

A sub dial is a small dial used for several purposes, such as keeping track of elapsed minutes or hours on a chronograph, or to indicate the date.


A label used to indicate that a wrist watch is made in Switzerland. By current Swiss law, a watch is considered completely Swiss-made if it contains a movement that is Swiss, if the movement itself is encased in Switzerland, and if any final quality control by the manufacturer occurs in Switzerland.

Swiss Movement:

The movement of a watch with Swiss movement has been assembled in Switzerland, the Quality Control check is completed in Switzerland, and the components of Swiss parts make up at least 50 percent of the total value, minus the cost of assembling the movement.

Tachometer (Tachymeter):

A tachometer is an instrument for measuring speed or units. In watch making, a timer or chronograph with a graduated dial shows speed in kilometres per hour or some other unit.


A telemeter is a watch function that finds the distance of an object from the wearer by measuring how long it takes sound to travel that distance. Like a tachometer, a telemeter consists of a stopwatch function and a special indication on the dial of a chronograph.


A timer is an instrument used for registering intervals of time without displaying the time of day.


Titanium is a "space age" metal, often having a silver-gray appearance. Because it is 30 percent stronger and nearly 50 percent lighter than steel, it has been increasingly used in watch making, especially sport watch styles. Its resistance to salt water corrosion makes it particularly useful in divers’ watches. Since it can be scratched easily, some manufacturers use a patented, scratch-resistant coating. Titanium is also hypoallergenic.


A tonneau watch has a barrel-shaped watch case and two convex sides.


A totalizer is a mechanism that keeps track of elapsed time and displays it usually on the watch’s sub dial. It is sometimes called a "recorder" or "register." The term "totalizer" can be used more generally to refer to any counter on a watch.

Unidirectional Rotating Bezel:

The unidirectional rotating bezel, or an elapsed time rotating bezel, moves only in a counterclockwise direction and is often found on divers’ watches. It is designed to prevent divers from overestimating their remaining air supply. Because the bezel only moves in one direction, the diver can err only on the side of safety when timing the dive. Many such bezels are ratcheted, so that they lock into place for greater safety.

Watch Winder (Watch Rotator):

A device used to allow the continuous running of automatic (self-winding) wrist watches when not in use. In general, automatic watches employ the use of a rotor, or a moving weight to wind itself when worn on the wrist. If the watch is not worn, there is no way to receive any additional power and the watch will eventually run out of its power reserve. While most automatic watches can be manually wound, a watch winder makes this process much easier, more convenient, and overall, safer for wristwatches, as there is no need to manually handle the watch.


Water-resistance describes the level of protection a watch has from water damage. A watch bearing the inscription "water-resistant" on its caseback can handle light moisture, such as a rainstorm 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 (165 feet) 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.


Waterproof: An illegal and misused term: No watch is fully 100% waterproof. Waterproof means the ability to completely exclude the possibility of water entering into any working portion of a watch. According to the Federal Trade Commission, no watch is fully 100 percent waterproof and no manufacturer that sells watches in the U.S. may label any of their watches as "waterproof." The FTC stipulates that watches be referred to as "water resistant."

Winding Stem:

The winding stem button resides on the right side of the watchcase and is used to wind the mainspring; it is also called a "crown."


Winding refers to the tightening of the watch’s mainspring. This can be done by hand (by the crown) or automatically (by a rotor, which swings due to movements from the wearer's arm).

World Time Dial:

A world time dial, usually found on the outer edge of the watch face, tells the time in 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 hour hand points to a city along a set scale enabling the wearer to determine the time zone. Watches with this feature are called "world timers."