A helpful glossary to assist you in deciphering most of the terms used by the watch industry and watch sellers today.

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30-Minute Recorder (or Register):
A subdial on a chronograph (see "chronograph") that can time periods up to 30 minutes.

12-Hour Recorder (or Register):
A subdial on a chronograph that can record time periods of up to 12 hours.

Accuracy:
Refers to rate constancy of a watch, not only on whether it is showing the exact time. A watch gaining or loosing exactly the same amount every day is considered accurate. It is considered “normal” for mechanical or automatic watches to gain/lose 4-6 minutes per day.

Acrylic Crystal:
Sometimes 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. Most watches produced since the 1930’s use acrylic crystals.

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

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

Atmosphere (Atm):
Unit of pressure used in watch making to indicate water resistance.

Automatic Movement / Automatic Winding (also called self-winding):
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.

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Band:
A 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.

Bezel:
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.

Bracelet:
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.

Buckle
The metal fastener found on leather straps. On some finer watches, the buckle can be “signed” with the watchmaker’s mark.

Bumper Automatic
Type of watch movement found only in vintage watches. It is similar to the rotor automatic which winds the watch based on the wearer's movements. The difference with the bumper automatic is the weight may have only a 180 degree or less path of movement--hitting a small bumper at each end of its path of travel, which provides a slight “bump” feel to the wearer.

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Cabochon:
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.

Calendar:
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. Sometimes referred to as a perpetual calendar.

Case or Watchcase:
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.

Chronograph:
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 time more than one event at a time (see "flyback hand" and "split seconds hand"). Not to be confuse with "chronometer" which is a timepiece that has met certain high standards of accuracy set by an official watch institute of Switzerland.

Chronometer:
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. Now, only a watch whose movement has been certified by C.O.S.C. can be called a chronometer. For a typical men's-sized mechanical watch movement, it must have stayed within -4 to +6 seconds of variation per day during the COSC measurement at various temperatures and positions.

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

C.O.S.C.:
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.

Crown:
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 time 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.

Crystal:
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 times harder than mineral crystals and 20 times harder than acrylic crystals.

Cyclops (Magnified Window):
A small window or lens in the crystal that is added to magnify the date 2 1/2 times.

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Day/Date Watch:
A watch that indicates not only the date but also the day of the week.

Deployment Buckle (Foldover):
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.

Dial:
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 time. 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.

Diver's Watch:
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.

Dual Time/Second Time Zone Bezel:
A rotating bezel, which can be used to display a separate time zone distinct from that shown on the dial.

Dual Time:
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, subdial, or other means.

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Elapsed Time Rotating Bezel:
A graduated rotating bezel (see "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. You can then read the elapsed time off of the bezel. This saves from having to perform the subtraction that would be necessary if you used the watch's regular dial.

Elapsed Time:
The actual time taken for an object to travel over a specified distance.

Engine Turning:
Decorative engraving, usually on a watch dial.

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Face:
The visible side of the watch or the dial.

Flyback:
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 times without losing the ability to capture the finish time.

Foldover Buckle (Deployment):
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.

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

Gold Plating:
An application of gold over the surface of an item.

Gold, Rose Gold, Yellow Gold, and White Gold:
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--by literally washing out the yellow color of the metal.

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Hack:
Feature on many mechanical movement watches that stops the second hand when you pull the crown all the way out to set the time. This makes it much easier to set a mechanical watch precisely to the second when synching with a time signal or known accurate clock. Older watches less commonly have this feature. To simulate the hack feature on many watches that don't have it, pull the crown out to the time setting position, then try gently turning the crown backwards. This puts a small amount of back pressure on the watch movement, which may stop the second hand long enough for you to synchronize it with another clock.

Hand:
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.

Handwinding (Manual Mechanical):
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.

Jewels or j:
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. While too few can certainly be a problem, the exact number needed for optimal performance depends on the specific design and features of the movement. Overall, 17 jewels is the lowest number needed for most standard mechanical watch movements. Others movements that implement different designs, or complications such a chronographs, may use more. But a novice cannot derive useful basis of evaluation or comparison from whether a watch has 17, 21, 25 or more jewels.

Jump Hour Indicator:
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 times 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.

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Karat or K:
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. 14K translates to 14/24=.583, or 58% pure.

Keeper:
The one or two loops included on watch straps, used to help hold any extra part of the strap protruding past the buckle.

Kinetic:
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.

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Lap Timer:
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 to begin timing the next lap.

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

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Magnified Window (Cyclops):
A small window or lens in the crystal that is added to magnify the date 2 1/2 times.

Manual Winding:
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.

Mechanical Movement:
A movement based on a mainspring which when wound slowly unwinds the spring in an even motion to provide accurate timekeeping. 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 time you move your wrist (see our section on automatic watch maintenance for more details).

Military or 24 Hour Time:
When time is measured in 24-hour segments. 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 any time from 13 to 24.

Mineral Crystal:
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.

Minute Repeater:
A Complication on a watch that can strike the time in hours, quarters, or seconds by means of a push piece.

Moon Phase:
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.

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 means by which a watch keeps time, 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 measures the vibrations in a piece of quartz and often is powered by a battery.

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O-Ring:
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.

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Perpetual Calendar:
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.

Platinum:
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.

Power Reserve Indicator:
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.

Power Reserve:
A measure of the amount of time 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 sometimes used to refer to the expected battery life--typically 12 to 32 months.

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

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

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Quartz:
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).

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

Rattrapante Chronograph:
The addition of a flyback 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.

Register:
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.

Repeater:
A device that chimes the time 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.

Retrograde:
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 time, pointing to the current date - when it reaches 31 it will spring back to 1

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

Rose (or Pink) Gold:
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.

Rotating Bezel:
A bezel (the ring surrounding the watch dial) that can be turned. Different types of rotating bezels perform different timekeeping and mathematical functions.

Rotor:
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.

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Sapphire Crystal:
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 collectors. The downsides are that sapphire can chip at the edges if they protrude and can shatter.

Screw-Down Locking Crown:
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.

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.

Self-Winding:
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.

Shock Resistance:
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.

Signed:
Any of various marks indicating the maker of the watch. Can be found on the dial, the crown, the movement, the back plate, the strap or bracelet, and the clasp. Some maker marks evolved over time and in some cases, the presence of an unsigned part (i.e. crown) does not necessarily mean that it is not original to the watch.

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

Stainless Steel:
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.

Sterling Silver:
A precious metal. Sterling 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 country of origin as a hallmark. A protective coating may be added to prevent tarnishing.

Stopwatch:
A watch with a seconds hand that measures intervals of time. When a stopwatch is incorporated into a standard watch, both the stop watch function and the timepiece are referred to as a "chronograph".

Strap:
A watchband made of cloth, rubber, leather or other non-metal material. Straps come in sizes (widths) which is the measured distance between the lugs. The most common size in vintage Swiss watches is 18mm.

Subdial:
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.

Swiss A.O.S.C. (Certificate of Origin):
A mark identifying a watch that is assembled in Switzerland with components of Swiss origin, primarily used in Bedat watches.

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

Tank Watch:
A rectangular watch with heavier bars on either side of the dial. Inspired by the tank tracks of World War I and first created by Louis Cartier.

Tantalum:
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.

Telemeter:
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.

Timer:
Instrument used for registering intervals of time (duration, brief times), without any indication of the time of day.

Titanium:
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.

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

Totalizer:
A mechanism that keeps track of elapsed time 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.

Turbillon:
A special complication found on only a few very high end mechanical watches that compensates for the effect of gravity. This eliminates the small variation in watch movement performance based on the position of the watch (face up, face down, on side, etc.).

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Unidirectional 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 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.

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Water Resistance:
Describes the level of protection a watch has from water damage. Due to FTC demands in the late 1960’s, the term "water resistant" became used to describe watches that used to be labeled “waterproof”. There are no technical differences between a waterproof watch and a water resistant watch--they use the exact same methods and technologies to keep water out. The difference is only in what term was considered to appropriate to describe it at the time it was made.

Waterproof:
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." As a result, the term "waterproof" was discontinued starting in the late 1960's. "Waterproof" was considered to have misrepresented the products as more capable of preventing the entry of water under normal use circumstances than they were actually capable of. Specifically, diving-type watches never have been completely 'proof' of water entry under normal use and within the stated depth ratings. The seals that keep water out are not completely impervious and their effectiveness can be reduced over time with age, deterioration, and exposure to chemicals.

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

Winding:
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).

World Time Dial:
A dial, usually on the outer edge of the watch face, which 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."

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