A subdial on a chronograph that can record t.mes periods of up to 12 hours.

A subdial on a chronograph (see "chronograph") that can t.mes periods up to 30 minutes.

Refers to rate constancy of a watch, not only on whether it is showing the exact t.mes . A watch gaining or loosing exactly the same amount every day is considered accurate.

Somet.mes s referred to as Hesolite, an acrylic crystal is composed of plastic composite that is generally less expensive and less durable than a sapphire or a mineral crystal. Benefits of an acrylic crystal are that it flexes rather than shatters on impact. It also produces little glare under bright light and can be polished easily.

A device that makes a sound at a preset t.mes . There are both quartz and mechanical alarm watches.

Function that provides altitude by responding to changes in barometric pressure, commonly found in pilot watches. Inside a pressurized airplane cabin, the alt.mes ter registers as if on land.

A watch with a dial, hands, and numbers or markers that present a total display of 12-hours.

A watch that shows the t.mes by means of hands (analog display) as well as by numbers (a digital display). The analog display has a traditional dial with hour, minute and somet.mes s second hands. The digital display shows the t.mes numerically with a liquid crystal display. This feature is usually found on sport watches.

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 - at the end of February to the 1st of March.

Small opening. The dials of some watches (in French: montres guichet) have apertures in which certain indications are provided (e.g. the date, the hour, etc).

Unit of pressure used in watch making to indicate water resistance.

Provided by the U.S. National Institute of Standards and Technology, t.mes and Frequency Division, Boulder, Colorado, atomic t.mes is measured through vibrations of atoms in a metal isotope that resembles mercury. The result is extremely accurate t.mes that can be measured on instruments. Radio waves transmit this exact t.mes throughout North America and some 'atomic' watches can receive them and correct to the exact t.mes . To synchronize your watch with atomic standard t.mes , call (303) 499-7111.

A mechanically powered watch that is wound by the motion of the wearer's arm rather than through 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 36 hours of power reserve. If an automatic watch is not worn for a day or two, it will wind down and need to be wound by hand to get it started again. Click here for automatic watch instructions.

A vague, generic term used to refer to the band that holds a watch on your wrist. The preferred terms bracelet and strap, clearly describe the two major types.

A device that converts chemical energy into electricity. Most watch batteries are the silver oxide type, delivering 1.5 volts. Much longer-lasting lithium batteries deliver 3 volts.

Battery End Of Life indicator. This function forewarns of impending battery failure in a quartz watch by means of the second hand jumping in two or somet.mes s four-second intervals. The wearer usually has approximately two weeks before battery failure.

The period of t.mes that a battery will continue to provide power to run the watch. Life begins at the point when the factory initially installs the battery in the watch.

Also known under various marketing names, including Kinetic (Seiko), Omega-matic (Omega), and Auto quartz (Invicta). Terms for the modern hybrid watch technology of using a quartz movement powered by a small electric current generator operated by a rotor. Electricity generated from the rotor's movement is stored in a capacitor, rechargeable battery, or similar means to keep the watch running. So, like an automatic watch, these also must be worn regularly to keep up their electrical power reserve.

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

A bezel that can be moved either clockwise or counterclockwise. These are used for mathematical calculations or for keeping track of elapsed t.mes .

A bracelet is the flexible metal band consisting of assembled links, usually in the same style as the watchcase. Detachable links change the length of the bracelet. Bracelets can be made of stainless steel, sterling silver, gold, or a combination. See also strap.

Control Officile Suisse de Chronometers or Swiss Controle Officiel des Cronometres- the independent Swiss regulatory organization that rigorously tests and certifies (or fails) watch movements for chronometer status.

Used to indicate a smooth round or oval convex shaped polished gemstone. In watch terminology, it describes a decorative stone set in the watch crown.

The calendar mechanism or function on a watch can consist of a date only showing in a window through to a triple calendar, showing the date, day and month. A combination of dial cut outs and pointer hands may be used. The most complicated calendar mechanisms may be mechanically programmed to show the year and months including those with less that 31 days; leap years can also be mechanically allowed for. Somet.mes s referred to as a perpetual calendar.

Case Diameter is measured without the taking the crown into consideration. All measurements are approximate.

The metal housing that contains the internal parts of a watch. Stainless steel is the most typical metal used, but titanium, gold, silver and platinum can also be used.

A multifunction sport watch with a stopwatch function. Most have two or three subdials, or minidials, for measuring minutes and hours. When used in conjunction with specialized scales on the watch dial it can perform many different functions, such as determining speed or distance ( see "tachometer" and "telemeter"). Some can t.mes more than one event at a t.mes (see "flyback hand" and "split seconds hand"). Do not confuse with "chronometer" which is a t.mes piece that has met certain high standards of accuracy set by an official watch institute of Switzerland.

The addition of a flyback hand (rattrapante) significantly increases the potential uses for chronographs. It makes possible the measurement of split second t.mes s or timing simultaneous events of unequal duration.

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 certifcate detailing specific test results by the C.O.S.C.

The attachment used to connect the two ends of the watch bracelet around the wrist.

A function that lets the wearer keep track of how much of a preset period of t.mes has elapsed. Some countdown t.mes rs sound a warning signal a few seconds before the t.mes 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.

The crown often referred to as the winding crown or winder is used for winding the watch in the case of a non-automatic, for setting the hands to the correct t.mes and often for setting the date in the case of calendar equipped watches. On diving/sports models, the crown may be screw-down whereby it screws onto a threaded tube, which protrudes from the case of the watch. This often ensures superior water resistance.

The cover over the watch dial is called the crystal. There are three types of crystals commonly used in watches: acrylic crystal is an inexpensive plastic that allows shallow scratches to be buffed out. Mineral crystal is composed of several elements that are heat-treated to create an unusual hardness that aids in resisting scratches. Sapphire crystal is the most expensive and durable, approximately three t.mes s harder than mineral crystals and 20 t.mes s harder than acrylic crystals. A non-reflective coating on some sport styles prevents glare.

Caseback made of transparent material such as hardened mineral crystal or sapphire crystal that reveals the intricate movement of the watch.

A small window or lens in the crystal that is added to magnify the date 2 1/2 t.mes s.

A watch that indicates not only the date but also the day of the week.

A three-folding enclosure that secures the two ends of the bracelet and allows enough room for placing the watch on the wrist when fully deployed. When closed, the buckle covers the two-piece folding mechanism.

An alarm on a diver's watch that sounds when the wearer exceeds a preset depth. In most watches it stops sounding when the diver ascends above that depth.

A device on a diver's watch that determines the wearer's depth by measuring water pressure. It shows the depth either by analog hands and a scale on the watch dial or through a digital display.

The dial, often referred to as the face is usually marked with numbers or batons to which the hands point in order for the wearer to tell the correct t.mes . Dials may be minimalist with no markers at all or extremely complex as in the case of pilots' chronographs. Dials may be decorated with patterns or in some cases with precious stones.

The display of t.mes in numbers instead of hands on the dial. The numbers can appear in an LCD (Liquid Crystal Display), which shows a continuous reading or an LED (Light-Emitting Diode), which shows the t.mes at the push of a button.

Indication of t.mes or other data, either by means of hands moving over a dial (analog display) or by means of numerals appearing in one or more windows (digital or numerical display); these numerals may be completed by alphabetical indications (alphanumerical display) or by signs of any other kind. Example: 12.05 MO 12.3 = 12 hours, 5 minutes, Monday 12th March. Such displays can be obtained by mechanical or electronic means.

Divers' watches traditionally feature a graduated, rotating bezel, screw down winding crown, and caseback... must be water resistant to at least 200m or 660 feet.

A watch that.mes asures current local t.mes as well as at least one other t.mes zone. The additional t.mes element may come from a twin dial, extra hand, subdial, or other means.

A rotating bezel, which can be used to display a separate t.mes zone distinct from that shown on the dial.

End of Life. In quartz movement, the end of battery life is indicated by the second hand, which starts to jump every four seconds. The battery should be changed immediately.

The actual t.mes taken for an object to travel over a specified distance.

A graduated rotating bezel (see "rotating bezel") used to keep track of periods of t.mes . The bezel can be turned so the wearer can align the zero on the bezel with the watch's seconds or minutes hand. You can then read the elapsed t.mes off of the bezel. This saves from having to perform the subtraction that would be necessary if you used the watch's regular dial.

Decorative engraving, usually on a watch dial.

The visible side of the watch or the dial.

An additional hand on a chronograph which moves with the second hand but, can be stopped independently to measure an interval which can then "fly back" to catch up with the other hand. This is useful for capturing lap t.mes s without losing the ability to capture the finish t.mes .

A three-folding enclosure that secures the two ends of the bracelet and allows enough room for placing the watch on the wrist when fully deployed. When closed, the buckle covers the two-piece folding mechanism.

GTNN (Greenwich Mean t.mes ), also known as Zulu t.mes , as set to the international clock in Greenwich, England, reflects, through an additional hour hand, the world t.mes on a 24-hour scale and is used by pilots worldwide.

A rubber or plastic ring that seals the internal works of the watch against dust, moisture and water.

An application of gold over the surface of an item.

The only natural form of gold is yellow gold. But since gold is too soft in its pure form to make jewelry, it is normally made into an alloy by mixing it with other metals. The portion of pure gold to other metals determines the Karat rating. 24K is pure gold. 18K is 75% pure. The exact nature of the other metals used determines the color. A moderate amount of copper in the alloy creates Rose Gold. A moderate amount of palladium and nickel creates white gold.

Indicator, usually made of a thin, light piece of metal, variable in form, which moves over a graduated dial or scale. Watches usually have three hands showing the hours, minutes and seconds.

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

The bearing, endstone or pallet used for reducing friction within the movement of a watch are made of synthetic material of precious or semi-precious stones. Usually a very inexpensive form of synthetic ruby, these are used for virtually frictionless pivots or hubs at certain critical places in the watch mechanism. These jewels do not add any monetary value to a watch. It is also important to understand that more jewels does not necessarily make a better watch.

A jump hour indicator takes the place of an hour hand. It shows the hour by means of a numeral in a window on the dial of the watch. The word "jump" refers to the fact that the numerals jump from 1 to 2 to 3, etc., rather than showing intermediate t.mes s between hours as hour hands do. The minutes and seconds in a jump hour watch are read as normal from the analog hands and dial.

An indication of the purity of the metal used, expressed in the number of 1/24th of the pure metal used in the alloy. Metals such as gold are too soft in their pure state use in jewelry, so they are typically made into an alloy with other metals for strength. 24K (equal to 24/24ths) is pure metal. 18K is 18 parts pure metal mixed with 6 parts of other metals. That translates to 18/24=0.750, which is 75% pure, or 750 parts per thousand.

Refers to the Seiko line of Kinetic watches. This innovative technology has a quartz movement that does not use a battery. Movement of your wrist charges a very efficient capacitor which powers the quartz movement. Once the capacitor is fully charged, men�s models will store energy for 7-14 days without being worn. Ladies models store energy for 3-7 days. The watch alerts you to a low capacitor charge when the seconds hand starts to move in two second intervals.

A digital watch display that shows the t.mes electronically by means of a liquid held in a thin layer between two transparent plates. Followed from the earlier LED or Light Emitting Diode display of the first quartz digital watches. The LCD was preferred as it used vastly less power than the LED thus the t.mes could be shown constantly as opposed to having to press a button for t.mes display.

The ability, in some quartz sport watches, to preserve in the watch's memory the t.mes s of laps in a race that have been determined by the lap t.mes r (see "lap t.mes r"). The wearer can recall these t.mes s on a digital display by pushing a button.

A chronograph function that lets the wearer t.mes segments of a race. At the end of a lap, the wearer stops the t.mes r, which then returns to zero to begin timing the next lap.

Extensions on both sides of the case where the bracelet or strap is attached.

A small window or lens in the crystal that is added to magnify the date 2 1/2 t.mes s.

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

A movement based on a mainspring which when wound slowly unwinds the spring in an even motion to provide accurate t.mes keeping. As opposed to a manual mechanical watch which needs to be wound on a consistent basis, an automatic mechanical requires no winding because of the rotor, which winds the mainspring every t.mes you move your wrist (see our section on automatic watch maintenance for more details).

When t.mes is measured in 24-hour segments. To convert 12-hour t.mes to 24-hour t.mes , simply add 12 to any p.m. t.mes . To convert 24-hour t.mes to 12-hour t.mes , subtract 12 from any t.mes from 13 to 24.

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

A Complication on a watch that can strike the t.mes in hours, quarters, or seconds by means of a push piece.

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.

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.

A Movement is the Engine of a Watch

The means by which a watch keeps t.mes , often including the power source. For example, a watch with mechanical movement uses a spinning balance wheel powered by a tightly wound spring, whereas a watch with quartz movement.mes asures the vibrations in a piece of quartz and often is powered by a battery.

O-rings are used to seal the backs of watches, which feature either a press-in back or a screw on back. They ensure water resistance. Usually also used on the winding stems of watches and in the winding crowns to protect against the ingestion of water and dust. Normally made from a rubber/plastic compound.

A device that counts the number of strides taken by the wearer by responding to the impact of the wearer's steps.

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

One of the most rare precious metals, platinum also is one of the strongest and heaviest, making it a popular choice for setting gemstone jewelry and watches. It has a rich, white luster, and an understated look. Platinum is hypoallergenic and tarnish resistant. Platinum used in jewelry and watches is at least 85 to 95 percent pure. Many platinum watches are produced in limited editions due to the expense and rarity of the metal.

A measure of the amount of t.mes a watch will run after being fully powered or wound, with no additional power input. Normally, this means when a mechanical watch is fully wound or a quartz watch has a brand new battery. 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 is somet.mes s used to refer to the expected battery life--typically 12 to 32 months.

A feature that shows when the watch will soon 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 seconds hand moving at two or three-second intervals. Seiko's Kinetic watches are quartz watches that do not have a battery (see Kinetic). When a Seiko Kinetic needs to be wound, the seconds hand will also move in two-second intervals.

A scale on a chronograph watch for measuring the pulse rate.

Button that is pressed to work a mechanism. Push-pieces are usually found on chronographs, striking watches, and alarms.

A caliber that uses the vibrations of a tiny crystal to maintain timing accuracy. The power comes from a battery that must be replaced about every 2-3 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 ( Kinetic & solar-tech).

A bezel ring that can either turn one way (counter clockwise) or both ways and generally clicks into place.

The addition of a flyback hand (rattrapante) significantly increases the potential uses for chronographs. It makes possible the measurement of split second t.mes s or timing simultaneous events of unequal duration.

Another name for a subdial; this is usually a dial within the main dial of a watch. The best example is possibly a chronograph where there may be registers for the chronograph minutes and hours. Some watches have registers with pointers showing the day and date.

A device that chimes the t.mes when the wearer pushes a button. Some repeaters, called "quarter repeaters" sound just 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 after the quarter; and still others called "minute repeaters", sound the hours, quarters and minutes.

Used to describe a pointer hand on a watch dial (often a subdial), which returns to zero at the end of a prescribed period. For example a watch may have retrograde date - in this case the hand moves up a scale a day at a t.mes , pointing to the current date - when it reaches 31 it will spring back to 1

Protective coating of metal with a thin layer of rhodium; hard, brittle metal which does not oxidize and is malleable only when red hot.

A softly hued gold that contains the same metals as yellow gold but with a higher concentration of copper in the alloy. A popular color in Europe, rose gold in watches is often seen in retro styling or in tricolor gold versions. Some 18k red gold watches achieve their color from additional copper in the alloy.

A bezel (the ring surrounding the watch dial) that can be turned. Different types of rotating bezels perform different t.mes keeping and mathematical functions.

The part of an automatic (or self-winding) mechanical watch that winds the movement's 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.

Synthetic sapphire formed for use as the crystal of a watch. Extremely scratch resistant (9 on the Moh scale), a sapphire crystal is the material of choice for many watch collects ors. The downsides are that sapphire can chip at the edges if they protrude and can shatter.

Highly scratch resistant crystal created by the fusion of sapphire and mineral glass crystal.

A crown that aids water resistance by sealing the crown to the case of the watch. The seal is achieved by the matching of a threaded pipe on the case with the crown's internal threads and gaskets, while twisting the crown to lock it into place.

An additional dial that can be set to the t.mes in another t.mes zone. It lets the wearer keep track of local t.mes and the t.mes in another country simultaneously.

This term refers to a mechanically powered watch that is wound by the motion of the wearer's arm rather than through 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 36 hours of power reserve. If an automatic watch is not worn for a day or two, it will wind down and need to be wound by hand to get it started again. Click here for automatic watch instructions.

As defined by the U.S. government regulation, a watch's ability to withstand an impact equal to that of being dropped onto a wood floor from a height of three feet.

A rotating bezel, or ring, around the outside edge of the watch case that is printed with a logarithmic scale and assorted other scales and is used in conjunction with fixed rules of mathematics to perform general mathematical calculations or navigational computations.

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 even in the dark.

Solar powered quartz watch. This technology provides the accuracy of quartz, without the inconvenience and cost of regular battery changes.

A feature on a chronograph that actually is two hands, one a flyback, the other a regular hand. To t.mes laps or different finishing t.mes s, the wearer can stop the fly backhand independently while the regular hand keeps moving.

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 even on case backs on watches made of other metals and is the metal of choice used to make high quality watchcases and bracelets. It is also hypoallergenic because it doesn't contain nickel.

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

A watch with a seconds hand that.mes asures intervals of t.mes . When a stopwatch is incorporated into a standard watch, both the stop watch function and the t.mes piece are referred to as a "chronograph".

A watchband made of cloth, rubber, leather or other non-metal material.

A small dial used for any of several purposes, such as keeping track of elapsed minutes or hours on a chronograph or indicating the date.

A mark identifying a watch that is assembled in Switzerland with components of Swiss origin, primarily used in Bedat watches.

Instrument for measuring speed or units. In watch making, a t.mes r or chronograph with a graduated dial on which speed can be read off in kilometers per hour or some other unit (see t.mes r).

A metal with a texture similar to titanium, but a color similar to gold. Used by Omega for the gold-like trim on certain titanium watches. Many of these watches are also available in titanium with real gold trim.

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

Instrument used for registering intervals of t.mes (duration, brief t.mes s), without any indication of the t.mes of day.

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 diver's watches. Since it can be scratched easily, some manufacturers use a patented-coating to resist scratching. Titanium is also hypoallergenic.

A watch with a barrel-shaped watchcase and two convex sides.

A mechanism that keeps track of elapsed t.mes and displays it, usually on a subdial on the watch dial. Same as a "recorder" or "register". The term "totalizer" can be used more generally to refer to any counter on a watch.

Universal t.mes Coordinated. A universal t.mes based on the Greenwich Meridian used by the military and in aviation. Greenwich Mean t.mes (GTNN ) can be considered approximately equivalent to Universal t.mes Coordinated (UTC). GTNN as such is now obsolete however, being replaced by UTC. Using this t.mes zone/standard avoids errors and problems associated with different t.mes zones and summer t.mes s operational in different countries.

An elapsed t.mes 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 only moves in one direction, the diver can err only on the side of safety when timing his dive. Many are ratcheted, so that they lock into place for greater safety.

Describes the level of protection a watch has from water damage. See the "water resistance" section for a description of the different levels.

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 "waterproof." The FTC demands that watches only be referred to as "water resistant."

Operation consisting of tightening the mainspring of a watch. This can be done by hand (by the crown) or automatically (by a rotor, which is caused to swing by the movements of the wearer's arm).

The button on the right side of the watchcase used to wind the mainspring. Also called a "crown."

A dial, usually on the outer edge of the watch face, which tells the t.mes up to 24 t.mes zones around the world. The t.mes zones are represented by the names of cities printed on the bezel or dial. The wearer reads the hour in a particular t.mes 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 t.mes rs."

A countdown t.mes r that sounds warning signals during the countdown for a boat race.