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Glossary A-Z



ALLOY a combination of one or more other metals or non-metals that often enhance its properties.

ALTIMETER function that determines altitude based on changes in barometric pressure. In a pressurized airplane cabin, the altimeter registers as if on land. A rotating bezel is used to determine altitude.

ANALOG WATCH watch that displays the time with hands and indexes, as opposed to digits.

ANALOG/DIGITAL WATCH has both a digital display and hands of a conventional analog watch.

ANGLAGE angled finish of main plate or bridge edges, typically at a 45 degree angle. It is used to finish the movement, as well as to eliminate sharp corners that would otherwise be damaged while the watch is working.

ANNUAL CALENDAR annual calendar displays the date, day of the week and month with only one manual adjustment required per year for February (except during a leap year).

ANTI-MAGNETIC (A/m) unaffected by magnetism. If the parts most affected by a magnetic field (balance, balance spring and escapement) are made of non-magnetic materials or the materials are blocked from magnetism by a soft metal cage, the watch is called anti-magnetic. Typically this type of watch has a soft iron cage around the movement to prevent magnetic fields from affecting the timekeeping, however, Omega has a movement where all the critical parte are antimagnetic so no soft-iron cage is needed.

APPLIED (same as "appliqué") numerals or symbols cut out and stuck to dial.

ARBOR the shafts that the wheels and pinions are mounted on.

ATELIER a workshop where wristwatches are assembled.

ATM a measurement of pressure called an (atmosphere). An atmospheric measure is the amount of air pressure at sea level that a watch can withstand. (1ATM= 1BAR= 10m= 33.3ft)

ATOMIC WATCH quartz watch that is controlled by a radio signal from a cesium atomic clock. The result is extremely accurate time that can be measured on instruments. (radio-controlled)

AUTOMATIC MOVEMENT self-winding watch whose movement is mechanical. A weight (the rotor) turns by the motion of your arm and winds the mainspring. The energy is transferred into mechanical energy that creates the watch movement. These watches can be shaken or manually wound if the power reserve runs out.


BALANCE SPRING (same as "hairspring") is one of the most important components of a mechanical timepiece. The balance spring is a fine spiral torsion used in mechanical wristwatches to control the rate of oscillation of the balance wheel, and thus the rate of the movement of the hands and accuracy of the timepiece. It is an integral part of the balance wheel, because it reverses the direction of the balance wheel causing it to oscillate to-and-fro (back-and-fourth). Considered the heart of a mechanical timepiece.

BALANCE WHEEL regulating organ of the watch, vibrating on a spiral hairspring. Lengthening and shortening of the balance spring makes the balance wheel go faster or slower to advance or retard the watch.

BAR thin metal rod fixed between the horns that attaches the bracelet or strap to the watch. Also called a lug or spring bar.

BARREL cylindrical box containing the mainspring of a watch. The toothed rim of the barrel drives the train.

BARREL SPRING this spring's tension controls the amount of energy transmitted to the measurement. Hooked to the barrel and arbor, when it is tensed it releases energy.

BEAT the number of times per second (BPS) or per hour (BPH) that a balance wheel goes through a full arc of motion or the vibrations per hour (VpH) (half oscillation, or "tick") of a movement.

BEVEL (same as "chamfering") groove cut at an angle that is either over or under, but not equal to 90 degrees (typically 45 degrees).

BEZEL the ring around the top of the crystal. Generally hold the glass or crystal in place. A rotating ratchet bezel moves in some watches as part of a complication. Rotating bezels either rotate clockwise (uni-directional) or both counter-clockwise and clockwise (bi-directional) to assist in calculations.

BOTTOM PLATE (same as "mainplate") supports the bridges, which are often on the top of the plate, the movement, the dial, and the holes where the jewels are inserted.

BRIDGE the balance cock is attached to the bottom plate with pins. Fixed to the main plate to form the frame of a watch.

BUTTONS push piece controls, usually at 2'oclock and/or 4'oclock on the dial to control specific functions such as the chronograph or the alarm.


CALENDAR a simple calendar is a complication that shows the date of the month. A day/date shows the date of the month and the day of the week. A complete calendar shows the day, date, and the month or moon phase.

CALIBER the size and configuration of a watch movement. The diameter of the movement measured in "Parisian lines," where 1=2.256mm.

CAMBERED curved or arched dial, bezel or sapphire crystal.

CASE container protecting the dial and movement consisting of the case band, case back, and bezel.

CASEBACK bottom of the watch that lies against your skin.

CHAMFERING (same as "beveling") of the edges plates, bridges or parts (typically to a 45 degree angle).

CERAMIC material used as a shield for spacecraft reentering the earth's atmosphere, high tech ceramic is polished with diamond dust to create a highly polished finish.

CHRONOGRAPH stopwatch function that uses sub dials to keep track of second, minutes, and hours.

CHRONOMETER A chronometer is a high-precision watch capable of displaying the seconds and housing a movement that has been tested over several days, in different positions and at different temperatures, by an official neutral body (COSC). Each chronometer is unique, identified by a number engraved on its movement and a certification number given by the COSC. Each movement is individually tested for several consecutive days, in 5 positions and at 3 temperatures. Each movement is individually measured. Any watch with the denomination "chronometer" is provided with a certified movement. Generally accurate to 5 seconds per day, or better.

CO-AXIAL ESCAPEMENT is a type of modern watch escapement mechanism invented by English watchmaker George Daniels. Considered by many to be one of the most significant horological advancements since the invention of the lever escapement, the co-axial escapement functions with virtually no lubrication thereby eliminating one of the shortcomings of the traditional lever escapement.

COLUMN WHEEL upright castle shaped wheel in a chronograph that acts as a sliding link to operate the various levers that set the chronograph functions in motion, generally more accurate type of chronograph.

COMPLICATION any "function" added to a watch, such as a minute repeater, countdown timer, stop watch, altimeter, asthometer, pulsometer, calendar, moon phase indicator, split second chronograph, power reserve indicator, alarm, etc.

COTES DE GENEVE (also called "Geneva Stripes" or Glashutte Ribbing) A form of decoration in higher grade watch movements the consists of vertical stripes that are often applied to the bridges, main plate and other parts.

COTES CIRCULAIRES (also called "fausses cotes decoration") It is a similar decoartion to Geneva stripea but instead of vertical lines in consists of circular, concentric lines.

C.O.S.C. Controle Officiel Suisse des Chronometres (Official Swiss Chronometer Testing Institute) they test watches for several consecutive days, in 5 positions and at 3 temperatures. They either pass or fail the watch movement. If the watch passes it is certified as a "chronometer".

COUNTDOWN TIMER function which measures time remaining in preset period of time.

CROWN knob used to wind a mechanical watch and to set the time and/or calendar of a watch.

CYCLOPS small lens on the crystal to magnify the date.


DEAD BEAT SECONDS A hand that jumps when the second has elapsed. Generally, the jump of a hand is a distinctive feature of a quartz watch. In mechanical watchmaking, this is a function.

DEPTH ALARM a complication on a diver's watch that sounds an alarm when the wearer exceeds pre-set depth. The alarm stops when the diver ascends above pre-set depth.

DIAL face of the watch that generally displays hours, minutes, and seconds.

DIGITAL watch that uses an LCD or LED to display a continuous reading.

DISPLAY BACK it is a caseback that is transparent so that movement may be viewed. (also called: clear, see-thru, skeleton, exhibition)

DIVE WATCH designed especially for divers whose lives depend on the reliability of their watch in the water.

DLC (Diamond Like Carbon) a metal coating that produces a grey/black finish that is very scratch resistant and corrosion resistant. This type of coating is like PVD, but even harder (and more expensive).

DUAL TIME ZONE measures local time as well as time in another time zone.


EBAUCHE (raw movement) unassembled movement, without escapement, balance, hairspring, or mainspring.

EQUATION OF TIME The equation of time is the difference between true solar time and mean time. True solar time, given by sundials, varies from day to day because of the Earth's elliptical orbit, and according to the longitude of the point of observation. Mean time, given by watches, ignores these variations and for every day of the year mathematically divides time into equal hours. Apparent solar time, can be ahead (fast) by as much as 16 minutes 33 seconds (around 3 November), or behind (slow) by as much as 14 minutes 6 seconds (around 12 February).

ESCAPEMENT mechanism made up of the escapement wheel, lever, and discharging roller, which act to control the wheel movement and to provide pulses to pallets and thus the balance. Converts the energy of the mainspring into equal units of time. The escapement controls the amount of power released from the mainspring. The regularity is controlled by the balance and it's spring. The escapement controls the rotation of the wheels and thus the motion of the hands. It is fitted at the end of the gear train and is designed to interrupt the movement of the wheels at regular intervals. (The escapement is the source of the ticking sound in watches and clocks.)

EXHIBITION BACK (or "display" back) has a sapphire crystal on the caseback to view the movement.


FLANGE ring that separates the crystal from the dial.

FLYBACK function that allows a chronograph to be reset to zero without having to stop the chronograph first.

FOUDROYANTE small dial that is marked 0-8. The hand on the dial completes a sweep every second which is an elapsed time of 1/8th of second for each number.

FREQUENCY (also referred to as vibrations per hour - VPH, or beats per hour BPH) 18,000 VPH or 2.5Hz, 21,600 VPH or 3Hz, 28,800 VPH or 4Hz, 36,000 VPH or 5Hz, 43,200 VPH or 6Hz, 72,000 VPH or 10Hz

FUNCTION the same as a complication on a mechanical watch, but technically called a function on a quartz watch.

FUSEE grooved pulley that equalizes the mainspring by controlling its winding or unwinding.


GASKET most water resistant watches are equipped with gaskets to seal the caseback, crystal, and crown from water. Gaskets need to be checked every couple of years to maintain water resistance.

GEAR TRAIN made up of the going barrel, which drive the center wheel. The center wheel drives the third wheel then the 3rd wheel drives the second wheel. The second wheel drives the escapement wheel. It is the system of gears that transmits power from the mainspring to the escapement.

GENEVA SEAL quality seal the displays the City of Geneva coat of arms. Watches must meet eleven strict criteria to be awarded the Geneva seal.

GERMAN SILVER German watch manufacture A. Lange & Sohne uses untreated German silver in their movements. German silver has a brighter and more luxurious finish, as compared to brass (which is commonly used for base plates).

GLUCYDUR copper and glucinum stainless, non-magnetic alloy used in watch making for internal parts. Anit-magnetic alloy that expands very little when exposed to heat. (Used for balances)

GMT Greenwich Mean Time (GMT), a watch that has the capability of displaying two different time zones.

GUILLOCHE is a decorative engraving technique in which a very precise intricate repetitive pattern or design is mechanically engraved into an underlying material with fine detail


HACKING a feature that stops the second hand when the stem is pulled out as far as it will go and allows you to set the exact time.

HAIRSPRING (same as "balance spring") is one of the most important components of a mechanical timepiece. The balance spring is a fine spiral torsion used in mechanical wristwatches to control the rate of oscillation of the balance wheel, and thus the rate of the movement of the hands and accuracy of the timepiece. It is an integral part of the balance wheel, because it reverses the direction of the balance wheel causing it to oscillate to-and-fro (back-and-fourth). Considered the heart of a mechanical timepiece.

HALLMARK a mark stamped into the case of the watch to provide information about the degree of purity of the metal used, the country of origin, the year of manufacture, the identity of the case's maker, trademarks, reference numbers, and/or serial numbers.

HAND watches generally have three hands for seconds, minutes, and hours. They come in many different shapes: Pear, Breguet, Baton, Arrow, Skeleton, Luminous, Alpha, Dauphine and more.

HAND-WOUND WATCH a watch that receives energy by hand winding the crown.

HARDBACK a solid metal caseback.

HELIUM ESCAPE VALVE a helium escape valve is required for divers who spend a long time in hyperbaric chambers and breath helium enriched gas. The helium molecules are lighter than air and can therefore penetrate the watch. When a pressurized enclosure, such as a diving bell, surfaces and is depressurized the helium rushes out of the watch so quickly that the crystal on the watch pops out. To avoid this the helium escape valve releases this helium from the watch while resurfacing. This allows helium to escape without water entering the watch.

HORNS part of the case where the bracelet is attached by lugs or pins.

HOROLOGY science of time measurement, including the art of designing and constructing timepieces.


INCABLOC a brand of shock absorber for mechanical watches designed to protect pinions or jewels.

INDEX instead of a number, a marking indicating the hour and/or minutes.

INTERNAL BEZEL a bezel inside the watch case usually with a separate or additional crown.

ISO 22810 Water resistant standard for a watch company to state "water-resistant" it must withstand overpressure of at least 2 bars or 20 meters.

ISO 6425 Dive watch standard Divers' watches must be water resistant to 330 ft minimum (100 meters). They must also feature a time controller and comply with standards provided by NIHS 92-11 (ISO 6425) : luminosity, shock resistance, anti-magnetism, band solidity.


JEWELS (also called "rubies") synthetic sapphires or rubies that are used in a watch movement to reduce friction. They help maintain the watch's lubrication. More jewels does not necessarily denote higher quality.

JUMP HOUR a display in which the hour, shown through an aperture, instantly changes every 60 minutes.


LUG (same as "horn") part of case where bracelet or strap is attached.


MAIN PLATE (or "baseplate") the plate on which all other parts of a watch movement are mounted. metal piece that holds up the bridge and other parts of the movement. The bottom side is the dial side the top side is the bridge side.

MAIN SPRING the driving flat-coiled spring of a watch contained in the barrel or barrels that supplies power. This is what is wound, by hand or via an oscillating weight, and then unwound to power a watch.

MANUAL WIND a hand wound mechanical watch (no oscilatting weight, all power must be generated manually).

MANUFACTURE a factory that makes its own components and assembles at least one complete movement (caliber), in-house.

MARINE CHRONOMETER a highly accurate timepiece enclosed in a box that is used for determining the longitude on board a ship. A marine chronometer is mounted on gimbals so that they remain in a horizontal position to maintain their precision.

MECHANICAL MOVEMENT describes a movement with a balance wheel. Wound by hand or rotor. Dates back to the 14th century about 130 parts, or over 500 for the most complicated watches.

Learn more about watch movements here.

METER a measurement used to measure water resistance. (10m= 33.3ft= 1ATM= 1BAR)

MINUTE REPEATER a highly complicated function that can strike the time in hours, quarters, or minutes by means of a push piece. Before the light bulb, minute repeaters allowed their owner to listen to the time without the need for light.

MOON PHASE displays: new moon, first quarter moon, full moon, and last quarter moon by means of a disk that rotates beneath a small aperture. The 29 and 1/2 day cycle of the moon.

MOVEMENT the "motor" of a watch or the machinery that turn the hands, change the date, start/stop the chronograph. There are two classifications of movement, either mechanical or quartz electronic. (Go to the "movements" page for more info.)


NON SCREW LOCKED CROWN a crown that does not lock, less water-resistant than a locking crown.


OBSERVATORY CHRONOMETER- similar to a standard chronometer, but even more accurate. The movements are adjusted in 5 positions and generally must perform within a deviation of 0.6 seconds per day. Historically these were used at scientific observatories, and for expeditions where accuracy is paramount.

OSCILLATING SYSTEM hairspring and balance form the oscillating system. Two vibrations of the balance make the tick-tack sound of a mechanical watch known as oscillation. The travel of the balance wheel from one extreme to the other and back again.


PALLADIUM a rare and lustrous metal that is slightly whiter than platinum and slightly harder. It is part of the platinum group of metals. Palladium is tarnish resistant, electrically stable and resistant to chemical erosion as well as intense heat.

PALLET meshes with the teeth of the escapement wheel and transmits an impulse to the balance.

PERLAGE perlage is a surface decoration comprising of an even pattern of partially overlapping dots applied with a quickly rotating grinding drill tip. It consists of small, overlapping circles, and is typically applied to the main plate or bridges.

PERPETUAL CALENDAR extremely elaborate complication that keeps track of the day, month, date, and sometimes even the moon phase, zodiac signs, decade, century, and which adjusts for the length of the month and for leap years. (Accurate until 2100)

PINION small toothed wheel usually made of steel with a small number of teeth that mesh with gear train wheels.

PLATINUM one of the rarest precious metals as well as one of the strongest and heaviest.

POLISHED brilliant meal surface obtained on the watchcase with a fine abrasive.

POWER RESERVE INDICATOR a sub dial used to show how much power remains before the watch stops.

PROFESSIONAL WATCHES purpose built watches designed to be utilized in professional situations such as: diving, flying and exploring (sometimes referred to as tool watches).

PVD (Physical Vapor Deposition) method of coating watch cases by integrating titanium particles and then depositing gold for color. Generally comes in black finish, but other colors can be created. (Very similar to "titanium carbide".)


QUARTZ a natural or synthetic silicon dioxide crystal used in quartz analog or solid state digital watches when activated by a battery or solar power, the thin silver of the crystal very predictably vibrates at an extremely high frequency (32,768 times per second) step motor, electric circuit block.

QUICK SET DATE mechanism to set the date directly to avoid having to turn the hands over 24 hours.


RATTRAPANTE addition of a second hand to measure split times. (Also called split-second chronograph.)

REGULATOR the device inside a watch that speeds it up or slows it down to allow the more precise setting of the watch.

REGULATOR DIAL a watch where the hour and minute hands are not on the same, but separate, pinions. Generally a "regulator watch" (not to be confused with "retrograde") has an hours subdial at 12 o'clock, a seconds subdial at 6 o'clock and a central seconds hand.

REPEATER strikes the hour, half hour, minutes, seconds, or some combination of the two.

RETROGRADE an hour, minute, seconds or calendar hand which moves across a scale and, at the end of its cycle, returns immediately to zero to begin again (not to be confused with "regulator dial").

RHODIUM PLATING rhodium or gold plating is used on many high-end movements.

ROTOR part of an automatic watch that winds the mainspring. A flat piece of metal swivels on a pivot with the motion of the wrist. Its rotation continually winds the mainspring of the watch. It turns freely in both directions and uses the force of gravity to wind the mainspring.

RUBIES (also called "jewels") very hard jewels, usually synthetic, which are used to prevent wear on the gear train parts.


SAPPHIRE CRYSTAL synthetic corundum crystal with a hardness second only to a diamond. Transparent sapphire is used for a scratchproof watch glass. Made of crystallizing aluminum oxide at very high temperatures. Chemically the same as natural sapphire, but colorless. It is hard and brittle so it shatters easier than plexiglass or mineral glass. 9 on a mohs scale, a diamond is 10.

SCREW BACK caseback has a thread so that it can be screwed-in to the case.

SCREW-DOWN CROWN seals the crown against the case to prevent water penetration.

SEAL synthetic gaskets that seal the joints between parts of the case and keep out the water.

SHOCK ABSORBERS spring devices in balance wheel bearings that divert shocks away from the fragile pivot to the sturdier parts of the balance staff. The springs allow the balance wheel to return to its original position after shocks.

SHOT BLASTING a satin finish obtained by using tiny glass pellets, one or two microns in diameter.

SKELETON MOVEMENT/DIAL movement on a watch where the plates have been removed or trimmed so that you can see the gears and other parts.

SLIDE RULE BEZEL a rotating bezel 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.

SOLAR POWERED batteries are recharged via solar panels on the watch face. (Citizen ECO-Drive)

SOLAR TIME solar time, given by sundials, varies from day to day because of the Earth's elliptical orbit, and according to the longitude of the point of observation.

SPLIT-SECOND CHRONOGRAPH a split seconds chronograph (or "rattrapante" or "doppelchrono") has two seconds hands, the first push starts both hands together, the second push stops one hand while the other continues, and another push allows the stopped hand to catch up with the moving seconds.

SPRING BAR a spring loaded metal bar mounted between the case lugs used to attach the strap or bracelet.

STAINLESS STEEL extremely durable metal alloy consisting of steel, nickel, and composed mainly of chromium. It is virtually rustproof. It is also antimagnetic. 316L is the standard steel used in watchmaking, however Rolex uses a slightly harder and more corrosion resistant steel called 904L. 904L is generally used in chemical applications and it costs significantly more than 316L steel.

STEM the shaft that connects to the movement's winding mechanism, the crown is fitted to the opposite end.

STOP SECOND (same as "hacking") crown which can be pulled out to set the seconds on a watch accurately.

STOPWATCH a watch with a seconds hand that 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 DIALS auxiliary dials or registers.

SUPERLUMINOVA photo-luminescent non-radioactive material with a long period of phosphorescence.

SWISS MADE legally protected indication of Swiss origin. Under terms of the Swiss Federal Council ordinance of December 23, 1971, it can apply only to watches with: -Swiss Movement -Assembled in Switzerland -Final inspection must be done in Switzerland

SWISS MOVEMENT in order for a watch to state that it has Swiss Movement it must: -be assembled in Switzerland -be tested in Switzerland -have 50% of the parts from Swiss origin


TACHOMETER instrument for measuring speed over a measured distance. A racing car covers 1 mile in 30 seconds. The sweep second hand, when stopped at the end of the mile, would point to the 120 on the tachometer. The average speed in 120mph.

TANTALUM a grey, heavy, and very hard metal. Tantalum is used to make avariety of alloys at high melting point and high strength. Tantalum is completely immune to body liquids and is a non-irrititating material.

TELEMETER stopwatch or chronograph function with a scale that measures the distance of something from the wearer of the watch through the amount of time it takes for sound to travel.

TIDEGRAPH tides are the periodic rise and fall of the water of oceans, seas, bays and other bodies of water caused mainly by the gravitational interactions between the Earth, Moon and Sun. Tides rise and fall about every six hours. The tide graph indicates tidal movement based on the Moon's transit over the meridian and the lunitidal interval. (Also called Tide Function)

TIME ZONE the world is divided into 24 time zones spaced at intervals of 15 degrees in longitude. The zones start at 0 with Greenwich. Within each time zone, the hour and minute of the day is defined to be the same. Time zones are usually specified by the number of hours they differ from GMT. EST is GMT 5 hours.

TITANIUM a metal, gray in color, that is used for watch cases and bracelets. Much stronger and lighter than stainless steel and hypo-allergenic. It is 30% stronger and 50% lighter than steel. It is very resistant to salt water corrosion, making it useful for diver's watches. Although, since it can be scratched easily, some manufacturers use a coating to resist scratching.

TOURBILLON (also called "whirlwind") eliminates errors of rate due to earth's gravity of vertical positions. A complex mechanism requiring the highest watch making skills: consists of a mobile carriage carrying all the parts of the escapement. It is a regulating device which corrects for the gravity-caused differences in run time in a mechanical watch. (Shifts of weight)


UNI-DIRECTIONAL BEZEL a bezel that rotates only one way (a dive bezel, for example, only moves one way, because it is used to count how much air is left in your tanks, and you would not want your bezel to accidentally go back, because it could be extremely dangerous if you stay under too long).


VPH (Vibrations Per Hour) movement of a pendulum limited by 2 extreme positions. The balance of a mechanical watch generally makes 5 or 6 vibrations per second (18,000-21,600 per hour.) A high frequency watch makes 8-10 vibrations per second (25,200/28,800/36000/43,200 per hour) Vibrations per hour is also called BPH ("beats per hour").


WATERPROOF no watch is 100% waterproof.

WATER RESISTANCE ability of a watch to withstand water from entering the case. Common water-resistance measurements (1 ATM = 1 BAR = 10 METERS = 33 FEET). An ISO 22810 "water-resistant" designated timepiece must withstand overpressure of at least 20 meters. An ISO 6425 "dive watch" must be water resistant to at least 100 meters.

WHEEL circular part revolving an axis to transmit power or motion: first wheel, center (second wheel), third wheel, fourth wheel and escape wheel.

WORLDTIMER a timepiece that displays the current time in any part of the world, from 24 up to 37 timezones.


YACHT TIMER a countdown timer that sounds warning signals during the countdown to a boat race.