An alarm is a watch function that emits a sound or vibration at a predetermined time.
A/h or ALTERATIONS (or ALTERNANCE) PER HOUR
Also referred to as "A/h" or "Alternation per hour." A watch movement's frequency is measured in Hertz (Hz) or vibrations per hour (vph), also known as A/h. A single balance wheel swing corresponds to one vibration in a watch movement with a balance wheel. A vibration is half of an oscillation, also known as a semi-oscillation. Therefore, one swing of the balance wheel in either direction, such as clockwise, is one vibration or semi-oscillation, and two swings, such as clockwise followed by counterclockwise, is an oscillation. Read the complete description at vibration or vph.
An altimeter measures altitude or height above sea level. Recording ascent and descent, an altimeter watch is an essential piece of equipment for climbers, walkers, mountaineers, and, of course, aviators.
Amplitude is the degree-based measurement of the amount of rotation in the balance wheel's swing in either direction. The balance wheel of a running watch oscillates or rotates both clockwise and counterclockwise. Every swing in either direction is referred to as a "beat." The amplitude is the number of degrees of beat rotation. When a watch is lying flat or in the "dial-up" or "dial-down" position, the amplitude is typically more significant, ranging between 270 and 315 degrees. When the watch is vertical, amplitude typically decreases due to increased friction. The amplitude can also decrease as the watch winds down and the mainspring delivers less force. An amplitude that is too high or too low, or that varies too much in different positions, can indicate a problem with the movement.
See Day/Night Indicator
A quartz watch with both analog and digital displays. Read the “Analog” and “Digital” definitions to learn more.
Displaying the time by means of hands rotating around a dial. Compare with “Digital”.
Same as “lever escapement”.
Beveling or creating an angled edge on a bridge or other movement component. Anglage is accomplished either mechanically with a pantographic engraver or manually with a hand-held file. Ideally, each edge's angle should measure exactly 45 degrees. High-quality movements typically exhibit anglage.
An annual calendar complication displays the day, date, and month with minimal modification. The complication ensures that the correct date is always displayed by automatically adjusting for 30- and 31-day months. Thus, It must be reset annually at the end of February because it does not "know" whether February has 28 or 29 days in any given year. Compare with the "Perpetual Calendar."
A very tough ceramic coating that is electrolytically applied to aluminum, giving the metal its distinctive appearance. This coating process allows producing various colors.
Protected from the effects of magnetic fields, which can affect the precision of a movement by compromising the oscillation rate of the balance. A method of protecting against magnetism is to construct the balance and balance spring from metals that cannot be magnetized or are resistant to magnetization (e.g., Elinvar or Nivarox hairsprings used in conjunction with brass, nickel, or beryllium bronze balances). In addition to the lever, escape wheel, and impulse roller, other delicate components, such as the lever, can also be made of non-magnetic metals. A second method of protecting against magnetism is to encase the entire movement in a highly conductive alloy, which prevents magnetic fields from accumulating within it. A watch is considered antimagnetic if it continues to run within a magnetic field of 4,800 A/m (amperes per meter) with a deviation of no more than 30 seconds per day. A tendency for a watch to run slowly is indicative of its having been magnetized. Using a choking coil, a watchmaker can "cure" (i.e., demagnetize) a magnetized watch.
A specialist in the art and science of horology with a particular interest in antique timepieces.
It is a small opening/window on the dials of some watches that displays specific information, such as the hour and the date.
Applied indices are created by separating the index from the dial. This permits a variety of designs, including layered designs with multiple components per index. After the indices have been crafted, they are typically glued or pinned to the watch dial.
Any of the following numbers: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. By around AD 1200, Arabic numerals had reached Western Europe via Arabia, replacing Roman numerals, but they were most likely invented in India.
A synonym of axle (barrel arbor). A wheel with teeth is attached to an arbor, which is typically cylindrical, and both rotate.
Art Deco is a movement in the decorative arts and architecture that began in the 1920s and flourished in the 1930s in western Europe and the United States. It was first exhibited at the 1925 Paris Exposition Internationale des Arts Décoratifs et Industriels Modernes, from which it derives its name. The style is characterized by simple, clean forms, often with a "sleek" appearance. In fact, the Art Deco movement influenced the majority of the tonneau, barrel, and rectangular watches.
The depth of a watch's resistance to water and pressure. A watch with a rating of 1 ATM is waterproof up to 10 meters, which is equivalent to 30 feet.
Auto Repeat Countdown Timer
A countdown timer that resets and restarts after the predetermined time has elapsed. The countdown continues indefinitely until the stop button is pressed.
Automatic-Winding Movement Aka “Self-Winding Movement”
Automatic movements, also known as "self-winding," capture energy through the wearer's natural wrist motion. The popularity of watches with automatic movements stems from the fact that the wearer does not need to wind the watch daily to ensure proper operation. If the watch is regularly worn, it will maintain its power without needing to be wound. An automatic movement functions similarly to a manual movement, with the addition of a rotor, a metal weight. The rotor is coupled to the motion and can freely rotate. The rotor spins with each wrist movement, transferring energy and automatically winding the mainspring.
A rectangle-shaped diamond or gem.
Like the pendulum in a pendulum clock, a balance or balance wheel is a timekeeping component used in mechanical watches and small clocks. It is a weighted wheel that rotates back and forth, with a spiral torsion spring known as the balance spring or hairspring returning it to its center position. It is propelled by the escapement, which converts the rotational motion of the watch gear train into impulses that are transmitted to the balance wheel.
Internal bridge holding the balance assembly in place.
A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulate the timekeeping. This is also known as the Hairspring.
The balance wheel's axle or shaft
A weighted wheel that oscillates, dividing time into equal segments. This is the regulating mechanism that controls the watch’s timekeeping accuracy.
When referring to watches, the band implies the bracelet or the strap.
A drum-shaped container that holds the mainspring in a mechanical watch, thus the watch power reserve. The size of the barrel directly affects the length of the power reserve. Some watches feature a Double-Barrel which allows for extra-long power reserve. The toothed rim of the barrel drives the train.
Basel is a city on the Rhine River in northwest Switzerland, close to the country’s borders with France and Germany. It is also in Basel that one of the most famous watch show in the world is held every year in April.
The vibration of a watch's tick lasts approximately one-fifth of a second. The escape wheel striking the pallets produces the sound.
The watch bezel is the ring that encircles and secures the crystal glass. It is one of the numerous watch case components. Bezels are typically made of metal, but they can also be made of ceramic. A bezel can be used to measure speed, distance, and elapsed time.
Bi-Directional / Uni-Directional Rotating Bezel
A bezel that can be rotated in one direction only and is used to monitor elapsed time. A ratchet mechanism is often in place to prevent it from rotating in the other direction. It is often found on divers’ watches to prevent the diver from running out of air by overestimating the remaining air supply if the bezel is accidentally moved from the original position. The fact that the bezel moves in one direction only is a fail-safe feature which means the diver can only underestimate the remaining air supply.
A Swiss word that refers to the high quality of a piece of work or an object. In French, it means “to make well.”
The metal strap that goes around the wearer’s wrist. A watch bracelet is typically made up of flexible, separate links that can be removed to adjust the bracelet’s length.
A watch designed specifically for the visually impaired. The crystal that would normally cover the dial is absent, but it has been replaced with protrusions that allow the hands and characters on the dial to be touched by the user.
Breguet Overcoil Hairspring
The Breguet Spiral is basically a flat hairspring with the exception that the end bends up over the top, anchoring the "pivot point" of the spring closer to its center, improving the watch's rate and reducing the wear on the balance pivots.
This is a flat, narrow metal piece that is attached to the plate at both ends and has a hole or holes drilled into it for jewels to hold a rotating pivot(s) o a moving part(s).
A term used for the first style of the automatic winding watch made by the Rolex Watch Co. in the 1930s. Its name is derived from its distinctively round and protruding case back. This one-of-a-kind bulging design was inspired by the need to accommodate the innovative self-winding "perpetual" movements, concealing the winding rotor beneath a highly domed screw-down case back.
A smooth, unfaceted gemstone cut in a convex shape. Cabochons are sometimes set on winding crowns for decoration.
A calendar watch, as its name suggests, displays calendar information, which may include the date, day, month, week, year, and moon phase. A time and date watch is a "simple calendar" watch.
This refers to a domed/arched crystal
Caliber or Calibre
A watch movement aka “caliber” or "calibre") is the engine of a watch that serves as the driving force behind the watch and its functions. This internal mechanism controls the hands and any complications. Today, the term generally refers to a specific movement, its origins, or its creator, and is usually denoted by a number or an alphanumeric name.
A type of repeater watch with three chime rods as opposed to two that are tuned to octaves.
The watch's case contains the movement and the dial. This safeguards them against normal wear and tear and the elements. They are available in numerous styles and materials.
It is the underside of a watch that usually lies under your skin. Some case backs are made of sapphire crystal to display the watch’s movement.
Center Sweep Seconds Hand
A seconds hand mounted in the center of the dial rather than in a subdial. The arbor of the center wheel is hollowed out to make room for the shaft of the seconds hand.
Circle on a watch dial, near the dial’s edge, bearing the hour, and sometimes minute, numerals or indices.
A chronograph is a complication that refers to a timepiece's timing functionality, more usually referred to as a stopwatch. It enables the wearer to record time intervals without interfering with the watch's normal time-telling function. The chronograph revolutionized timekeeping by allowing for unprecedented accuracy in timekeeping — from 1/100 of a second to 12 hours. While the concept of a chronograph is the same, there are three types of chronographs available today.
The standard chronograph is operated by one or two buttons (also called "pushers") that initiate, stop, and reset the chronograph. While all early chronographs had a single button, most modern timepieces have one or two pushers.
The flyback chronograph is a more complex chronograph that allows for the quick restarting of the timer function while the chronograph is still running. When the chronograph button is pressed, it stops, resets to zero, and then restarts.
Rattrapante, the French term for "split seconds," refers to an additional complication in a chronograph. The rattrapante chronograph has a second hand overlaid on the chronograph hand, allowing simultaneous measurement of multiple events.
A precise time-keeping device. A Swiss chronometer must meet strict criteria imposed by the C.O.S.C. (Controle Officiel Suisse des Chronomètres). Five distinct positions and temperature adjustments are required throughout the course of 15 days and nights.
High-quality escapement invented in the late 1700s for marine or box chronometers on ships to determine longitude. "Detent" escapements are the most popular.
The global standard for timekeeping. Each half-day is 1-12 hours. One for the day and one for the night. Also known as the Mean Solar Day.
A watch in which a coin is used as the case.
To turn a chronograph on and off, and to return the chronograph hands to zero, an upright, notched rotating wheel is used. Many chronographs utilize a technology called “cam switching” instead of column wheels.
Coordinated Universal Time (U.T.C.)
Official world time, independent of time zones.
Côte De Genève
A regular wave pattern obtained by engine-turning and polishing.
Any function performed by a watch movement other than telling time. Common complications include the chronograph, calendar, and GMT. Watches with several complications are known as Grandes Complications.
The official chronometer testing organization in Switzerland COSC “Controle Officiel Suisse des Chronomètres”. See Chronometer
This allows the wearer to know how much of a preset time has passed. Some Quartz versions sound a warning a few seconds before the pre-set time has elapsed.
The grooved button on the exterior of the case (often positioned on the right side of the case at 3 o'clock) that is used to adjust the time on most watches, as well as wind the movement in a mechanical watch, and sometimes performs other tasks, such as setting the date. The crown stem connects the crown to the movement. Crowns can be either push/pull or screw-down, with the latter contributing to the water-resistance of the watch.
This is the clear cover on the watch face (dial). It may be made of glass, plastic, mineral crystal, or sapphire crystal (a scratch-resistant synthetic material). Its purpose is to protect the watch face.
A small lens on the crystal to magnify the date.
Engraving on watch plates and bridges. Including etched and geometric patterns.
A dial aperture that displays the date on a timepiece with a calendar complication. A date wheel on the upper side of the movement spins once every 24 hours to display the date. In watches with these complications, similar windows can additionally display the day of the week, month, and occasionally the year.
A watch that shows both the day of the week and the date of the month.
Day/Night or AM/PM Indicator
A feature that indicates whether the indicated time is AM or PM. This feature can be found mostly (although not limited to) in watches with a GMT/Dual time display or a World Time Display to help know whether it is day or night in the other time zones.
Ornaments that have been added to the movement of a watch. Movements can be embellished by machine or by hand, with both ways boosting the manufacturing status and expense. Perlage, Côtes de Genève, and snailing are typical movement decorative techniques.
A watch case with a closed lid or cover over the dial and a small opening in the lid to read the time.
A buckle that attaches to either side of the strap. The buckle is expandable so that the watch can be slipped on the wrist & snaps shut on the wrist. Once set to the correct size it needs not be resized, thus reducing stress on the strap & elongates its life. This buckle also offers additional security while putting on & taking off the watch.
In Italian, it translates to “right”. It means that the watch was intended to wear on the right hand and is most associated with Panerai, Graham, and lately Rolex timepieces.
Locking internal movement part. A detent in a watch's setting mechanism could lock into the setting, winding, and possibly a quickset date position.
The dial, which is often referred to as the face, is the section of the watch that shows the time. In addition to brand and model information, the dial frequently displays information from various complications. It is available in a variety of colors, hands, and indices combinations.
A watch that shows the time in numbers, or digits, rather than hands and a dial. Liquid crystal display (LCD)is commonly used.
A pocket or wristwatch with a crystal case back to view the movement.
A setting position on the watch winding stem assembly that allows changing the date without moving the hands through a full day.
Dual Time Aka “GMT” or “Second Time Zone”
A Dual Time watch is extremely simple to use. It simultaneously displays two separate times for the wearer. The second timezone is typically displayed on a subdial in a 12-hour time period. See also GMT.
Duo Display Aka AnaDigi
A display that shows the time both by hour and minute hands (an analogue display) and by numbers (a digital display). This is also known as AnaDigi display.
An unassembled movement, without escapement, balance, hairspring, or mainspring.
A specially constructed movement that needs to be wound just once a week. In one eight-day movement, used in the Hebdomas wristwatch, introduced around 1913, the barrel covered the movement’s entire surface. Eight-day shaped movements from the 1930s had normal-size barrels, but each movement had two additional wheels added to its train. Eight-day movements are common in pendulum clocks and other larger timepieces.
Elapsed Time Rotating Bezel
A graduated rotating bezel that is used to keep track of periods of time. The bezel can be rotated so the wearer can align the zero with the watch’s minutes or seconds hand. The elapsed time can then be read off the bezel, rather than the wearer having to perform a subtraction necessary if he used the watch’s regular dial.
A battery-powered watch that vibrates a synthetic quarter crystal at 100 kilocycles per second. Electronic quartz watches are highly accurate.
This is a centuries-old craft that, still today, involves the use of antique machines to engrave delicate patterns on metal watch components, including cases, dials, bezels, and movements. It is also known as guilloche. See Guilloche
This hairspring is made of an alloy that doesn't change with temperature.
This is the End-Of-Life battery indication in Quartz-powered watches. Generally, the seconds begin to tick once in 4 seconds indicating that the power is low, and it is time to change the battery.
The time required for the Earth to orbit the Sun once.
Equation of Time
Sundial time versus Mean Time. Using a Sundial and conversion tables, an Equation of Time table can calculate Mean Time.
The final wheel in a train that works with a fork or lever to release one pulse at a time.
The device is at the heart of virtually all time-keeping mechanisms. It provides the impulses to maintain the oscillations of the balance wheel or pendulum which governs the rate at which the escapement lets the wheels and hands of the watch revolve.
The leading manufacturer in Switzerland for movements used in many Swiss brands.
Precise adjustment of a watch’s rate by means of a device such as a swan’s neck regulator or eccentric screw.
How the watch's surface has been treated. The term usually refers to the case and bracelet, but it can also refer to the condition of the hands, indices, or movement. Finishing techniques that are typically used include brushing and polishing.
A watch feature that allows you to record time in fractions of seconds and elapsed time with two separate recording hands while displaying normal time.
A small, decorative object worn on a pocket watch chain outside the pocket or vest.
The number of vibrations, or semi-oscillations, that a watch’s regulating organ makes per unit of time. Most modern mechanical watches have a frequency of 21,600 or 28,800 vph. Nearly all quartz watches have a frequency of 32,768 Hz.
A term used to describe the various tasks a watch can perform such as chronograph and countdown timer. These are also known as complications.
The gear train is the system of gears that transmits power from the mainspring of the watch to the escapement.
A quality seal awarded by an independent bureau in Geneva to watch movements submitted to it for inspection. To receive the seal, a movement must meet 12 criteria related to the quality of the movement’s finishing and the materials from which it is made. It must also have been manufactured in the canton of Geneva. The seal, which consists of the Geneva coat of arms, is stamped on the movement. The Geneva Seal is also called the “Geneva Hallmark” or the “Poinçon de Genève” (stamp of Geneva).
Decorative stripes on the plates, bridges, cocks, or rotors of many watches. Geneva waves are also called “Geneva stripes” or “côtes de Genève” (Geneva ribbing).
Special alloy composed of copper, zinc, & 10% nickel. The nickel minimizes the oxidation of German silver and thus eliminates the need to electroplate, and remain “untreated”.
A thin gold sheet (usually 20 microns thick) bonded to a base metal.
An electrodeposited layer of gold with a thickness that is measured in microns. “GP, HGE, GE” or any fraction after a number are stamps indicating a gold plate.
Unauthorized sellers of new watches.
A repeater that sounds the hours and quarter hours by pressing a lever. (Learn more: Repeater Watches)
Greenwich Mean Time Aka GMT, “Second Time Zone,” or “Dual Time Zone”
Greenwich Mean Time (GMT) is also known as Zulu Time and UTC (Universal Time Coordinated). The standard by which all World Time is set was agreed upon at the 1884 International Meridian Conference in Washington DC, USA. It placed Greenwich on the Prime Meridian (Zero Longitude). Greenwich Mean Time or GMT is the time standard against which all other time zones in the world are referenced. It is the same all year round and is not affected by Summertime or Daylight Savings Time. GMT was originally set up to aid naval navigation when the globe started to open with the discovery of the “New World” (America) in the fifteenth century. Generally, when the GMT term is used with watches it refers to the ability of the watch that shows local time and the time in at least one other time zone in a 24-hour mode. The reason for showing the additional time zone in 24-hour mode is to allow the wearer to know if the second time zone is AM or PM. See Dual Time, World Time.
Guilloche, also known as Engine Turning, is an engraving technique in which precise, intricate, repetitive patterns or designs are mechanically etched into an underlying material with a high degree of precision. It entails a process of engine turning known as guilloche in French, after the French engineer "Guillot," who invented a machine capable of scratching fine patterns and designs on metallic surfaces. See Engine Turning.
Also known as a hack or stop seconds. A watch that “hacks” or that has “hacking seconds” is one in which the seconds hand stops when the crown is pulled out. Hacking is typically achieved when pulling the crown out to the time-setting position causes a brake or lever to meet the rim of the balance wheel, causing it to stop and to be held in position. Hacking allows the watch to be more easily set to a reference signal or synchronized with second timepiece. Pushing the crown in releases the brake or lever, allowing the balance wheel to move freely.
A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulate the watch’s timekeeping. It is also known as a balance spring.
The mark stamped on the case of a watch indicates the purity of the precious metal used, the country (and sometimes city) of origin, the year of manufacture, and the case, maker. The watchmaker's logo, a reference number, and a serial number may also serve as additional identifiers.
The pointer that moves across the dial to indicate the hour, minute, and second. Typically, watches have three hands to indicate the hours, minutes, and seconds. There are numerous possible hand shapes, including leaf, stick, pear, Breguet, sword, skeleton, baton, and arrow.
A mechanical movement whose mainspring is wound manually by turning the crown; also known as a manual-wind movement. Compare with automatic movement.
A term used to describe the highest level of craftsmanship and complexity in mechanical watchmaking. Haute Horlogerie timepieces are the cornerstone of luxury brands and can be quite costly.
Helium Escape Valve
Professional Divers watches are created with deep-water divers' needs in mind. These divers routinely spend extended periods of time in pressurized diving bells, breathing Hypoxic trimix or other mixed gases containing helium. Because helium is such a small molecule (the second smallest), it will eventually penetrate the o-rings and enter the interior of a dive watch in a pressurized diving bell. While this does not pose a problem at depth, it will as divers decompress the helium, which cannot escape the watch. With a standard dive watch, internal pressure would cause the watch crystal to shatter. High-end, professional diver watches are equipped with a helium escape valve or helium bleed valve to release this excess pressure during decompression. The helium can escape through this one-way valve.
Also referred to as Hz. The frequency of a watch is measured using two different units: hertz (Hz) and vibrations per hour (VpH). Hertz refers to the number of oscillations a watch's balance wheel makes per second. See also VpH and vibration.
Arabic numerals, Roman numerals, or symbols that are placed around the dial to mark the hours.
A specialist in the art and science of horology.
The study of time measurement. Horology now primarily refers to the study of mechanical time-keeping devices.
Hunter Pocket Watch
A hunter-case pocket watch has a spring-hinged metal lid that closes over the dial and crystal to protect them from dust, scratches, and other damage.
A style of watch case with a spring-release button that opens and closes a lid or cover over the dial. This design is utilized for both pocket and wristwatch cases.
A type of shock-resistant system in which the jewels are held in place by springs. ). Incabloc shock absorbers can be recognized by their springs’ distinctive lyre shape. This gives the watch's balance a certain amount of "give" if it is subjected to a shock (Kif is another well-known brand of shock-absorber
A watch movement manufactured by the same company that produces the watch in which it is housed. As the creation of movements requires substantial Investments in research and development and investment, many watchmakers opt for readily available third-party movements. Therefore, watchmakers who produce their own movements are typically regarded as upscale.
A simple stick/line design hour indicator on an analog watch dial, used instead of numerals.
The friction-reducing internal component of a watch, such as a bearing. Typically composed of synthetic material, however, some watches of the highest quality feature both precious and semiprecious stones.
A jumping hour watch does not have a traditional hour hand that sweeps the dial once every 12 (or 24) hours, but rather a disc viewed through an aperture on the dial that jumps to display the next hour precisely when the minute hand reaches 60 minutes. Typically, minutes are displayed in a semi-circular aperture that contains multiple minute indications on a circular dial.
A unit used to specify the amount of pure gold in an alloy. Pure, unalloyed gold is 24 karat. Eighteen-karat gold consists of 75% gold and 25% other metals; 14-karat gold consists of 56% gold and 44% other metals.
Self-correcting device for vertical position timing errors. The escapement and balance are mounted on a carriage that rotates like a tourbillon, but more slowly.
Using a small key to set the hands of a keywind/keyset pocket watch Turning the key on the arbor sets the hands.
Use of a key and winding arbor to wind an antique watch.
A function in a chronograph watch that allows the wearer to time segments of a race. At the end of a lap, the timer is stopped and then returns to zero to begin timing the next segment.
Every four years, February 29 is added to the calendar to account for the quarter-day difference between a standard year (Mean Solar Year) and an astronomical year (Sidereal Year).
The abbreviation for light-emitting diode, is the type of display used in early digital quartz watches. The display lit up at the push of a button and was usually red.
The lever escapement, invented by British clockmaker Thomas Mudge in 1754 (but first used in 1769), is used in almost all mechanical watches, non-pendulum clocks, alarm clocks, and kitchen timers. This oscillation allows the timepiece's gear train to advance a fixed amount, thus moving the hands forward steadily. The escapement makes mechanical clocks and watches "tick."
A method for adjusting the hands of a pocket watch using a lever located beneath the bezel. Turning the winding crown sets the hands after the lever is pulled out.
A unit of measurement that is used to denote the diameter of the watch movement. One ‘ligne” is equal to 2.256 millimeters. The symbol for “ligne” is three apostrophe-like strokes, as in 1”’.
A timepiece produced in a limited quantity and is typically numbered to indicate its position in the series.
The segments of a watch bracelet. Connected to each other by either screws or push-pins, links need to be removed or added in order to size a bracelet to your wrist.
Liquid Crystal Display (LCD)
Liquid crystal display (LCD) watches show a numeric display continuously by means of the liquid held in a thin layer between two transparent plates. The numbers are made up of seven segments that form the number 8 when all are activated. They are activated by an electronic impulse.
The arms of the watch case that hold the strap or bracelet.
Luminous Hands and/or Hour Markers – is a standard feature on many watches. The hour markers and/or hands have a coating of “glow in the dark” which will illuminate in the dark so you can tell the time where there is insufficient light. Results vary by the amount & quality of Luminous material used.
The base plate upon which all other parts of a watch movement are mounted.
A mainspring is a metal ribbon spiral torsion spring that provides energy to mechanical watches, clocks, and other clockwork mechanisms. A watch is wound by turning a knob or key, which tightens the mainspring. As the mainspring unwinds, it turns the clock's wheels until the next winding.
A Manual watch operates by manually winding the crown which winds the mainspring in the barrel, thus powering the watch. Once wound it will stay working for the specified amount of time as indicated in your manual (generally 35-45 hours). See Automatic Winding Movement, Quartz Movement, Winding Crown.
A watch company that designs, makes components for, and assembles at least one of the calibers used in its watches.
A highly accurate mechanical or electronic timekeeper that is enclosed in a box and is used for determining the longitude on board a ship. Marine chronometers with mechanical movements are mounted on gimbals so they are in the horizontal position that is essential for their precision.
Mean Solar Day
The average number of solar days in a given year.
A feature that allows the wearer to convert one type of measurement into another. It usually consists of a graduated scale on the bezel or dial.
A “Mechanical Movement” is the term for a watch that runs without an outside electrical source. The watch’s mechanism is composed of multiple parts, gears, screws & springs. By winding the mainspring (either manual winding or automatic winding) the watch will begin to operate.
This is a thousandth of a millimeter and is a measurement used for the thickness of gold plating.
A winding rotor that is smaller than the rotors that wind most automatic watches. Unlike a standard rotor, which sits atop the rest of the movement, a micro-rotor is set into it. The movement is therefore thinner than it would otherwise be.
Glass that has been tempered to be more scratch-resistant. Used as a crystal material in lower-priced watches, mineral glass is far easier to scratch than sapphire, but it is more resistant to impact.
A watch that strikes the hours, quarters and minutes on gongs. The repeater is activated by a slide or button on the case edge. This is a highly complex achievement and increases the cost of the watch tremendously.
The markings around the outer edge of the dial, of which there are 60, that allow the hands to track minutes.
Mono (Single) Pusher Chronograph
A stop watch operated by a single button. While 99% of chronographs are operated by the use of two button – one to start & stop the stopwatch, the second to reset the stopwatch; a Mono Pusher complication allows for 1 button to start, stop & reset the stop-watch. See Split Seconds Chronograph a.k.a. Rattrapante, Fly-Back Chronograph
An indicator that shows what phase the moon is in. It consists of a disk printed with two full moons that rotates beneath an aperture on the dial. As it turns, portions of the moons become visible within the aperture, representing the real moon’s waxing and waning.
Mother of Pearl
The iridescent interior of a freshwater mollusk that is often used to decorate watch dials. Its colors include milky white, blue and pink. Mother of Pearl is available in an array of colors, such as blue, pink, yellow and more.
A wheel train that transfers the rotary motion of the center wheel arbor to the hour hand. In collaboration with the hand-setting system, the motion work, also called the “dial train,” also makes it possible to precisely set the positions of the hour and minute hands when the crown is pulled out and turned.
The motor of a watch that makes it keep time and perform functions. Specific models of movements are often referred to as calibers. See Automatic Wind Movement, Manual Wind Movement, Quartz Movement.
A watch with a music box-like mechanism that plays a melody every hour or on-demand.
Numerals (Roman and Arabic) are used to present information in the dial and subdials.
A dial style in which the sub-seconds of a watch are positioned to one side of the conventional 6:00 location.
The regular movement of a body, such as a balance wheel or pendulum, between two given points from one extreme to the other and back again. Anything that oscillates with regularity can be used as a timekeeper.
A case design in which the dial is exposed and not concealed by a lid or cover, as in a hunting case.
Rolex's designation for the movement of its waterproof self-winding watches
The designation given by Rolex to their waterproof watches.
One of the two small pins in a lever escapement that engages the escape wheel's teeth. Typically, pallets are made of synthetic ruby.
Age-related discoloration or oxidation of any surface.
A technique of setting stones so closely together that no metal is visible.
Attachment point for the bow and winding crown on a pocket watch.
Utilizing the stem and winding crown to set the hands on a pocket watch.
A complication showing the date, day, month & leap year cycle at the minimum. Many will also display the year & Moonphase. This watch will correctly adjust for short and long months as well as 28 days of February once in 4 years. See Annual Calendar, Moonphase.
The reduced or turned-down end of an arbor's branching structure. The three most common types of pivots are conical, cone, and shoulder-shaped.
This portion of the movement provides support for the other plates and bridges.
Platinum is one of the rarest and most durable of precious metals. It doesn’t tarnish and has a radiant, beautiful white luster. It is a popular choice for very prestigious watches & Limited Edition pieces.
A plastic material commonly used for crystals in vintage watches, and rarely in some modern ones. Plexiglass is very easy to scratch, but is highly impact resistant. Its scratches can also usually be buffed out using a compound, unlike other crystal materials. Plexiglass is also non-reflective and is often described as having a “warm” quality.
A pocket watch with an escapement of chronometer design.
A watch designed to be carried in one's pocket.
Power Reserve Indicator
An indication of the state of wind in the main spring. A hand on the dial points to the number of hours the movement will work before it runs down. Also known as Reserve de Marche
A scale on a chronograph which is used for measuring pulse rate.
A button that is pressed to work a watch function such as a chronograph, alarm or date corrector.
A complex timepiece that strikes the hours and quarter-hours.
Quartz is piezoelectric, meaning it generates an electrical charge under pressure. When a battery or other voltage source is applied, these crystals vibrate. Pierre and Jacques Curie discovered piezoelectricity in 1880. W.G. Cady realized in the 1920s that quartz crystals could be used to make stable resonators due to their elasticity, mechanical strength, and durability. Cady also concluded that specific crystal cuts could create resonators of almost any frequency that were virtually temperature independent. Warren Marrison, who invented the first quartz clock in 1927, used quartz crystals to keep time. In the 1970s, Juergen Staudte mass-produced quartz crystals for watches.
This is an electronic watch movement with a quartz crystal that oscillates when a current is applied to it. The power to run the watch is normally provided by a battery or a capacitor. A quartz movement is generally more accurate than a mechanical movement.
A setting position on the watch winding stem assembly that allows the date to be changed without advancing the hands through 24 hours.
A setting position on the watch winding stem assembly that allows the day or date to be altered without advancing the hands through a 24-hour cycle.
Rattrapante Aka “Split Seconds Chronograph”
See Split Seconds Chronograph
Regulator or Regulateur
A Regulator display presents the minute and hour hands on separate axial and sub-dials. This enables accurate time reading at a glance without the possibility of the watch hands overlapping.
The interior area of the case that sits below the crystal and forms a wall around the outside of the dial. Rehauts don’t often perform any function, but on some watches they feature logos (e.g. Rolex) or are home to the minute track.
A watch function or complication that strikes (chimes) the hours using an internal mechanism controlled by an external lever or button. There are numerous types of repeater designs. A minute repeater strikes the hours, quarter hour, and minutes after the preceding quarter hour. A repeating quarter-hour chimes the hours and quarter hours. A half-quarter-hour repeater strikes the hours and half-quarter hours that are closest. Five minutes past the hour, a five-minute repeater strikes.
A rectangular watch case that can be flipped or reversed within its main frame. One side displays the normal dial, while the other side displays either the back of the case or a different dial type, such as one for displaying dual-time.
A metallic element that is hard, white, and part of the platinum group. Often used to create platinum alloys. Used frequently in the production of watch cases and bracelets.
Reserve de Marche
See Power Reserve Indicator
A watch with a retrograde display does not display the function in a circular fashion, as we are used to seeing. Rather, it sets out the functions in a linear manner. Instead of the hands going round in a circle, they travel along an arc, and when they get to the end, they jump back to the beginning.
Rolled Gold Sheet
A thin gold sheet that is bonded to one or both sides of a base metal.
Style of numerals typically employed on watch dials (I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII).
A bezel around the watch that can be rotated. It has various timekeeping functions.
Rose gold is an alloy made from a combination of pure gold and copper. The blend of the two metals changes the color of the final product and its karat. For example, the most common alloy of rose gold is 75 percent pure gold to 25 percent copper, which makes 18k rose gold.
This is the oscillating part of an automatic watch that winds the mainspring.
A watch case design that is circular.
Sapphire crystal is a scratch-resistant transparent material. It is chemically identical to natural sapphire and ruby, but lacks the small amounts of other elements such as iron, titanium, and chromium that give the gemstones their colors. Sapphire is one of the hardest substances, measuring 9 on the Mohs scale, which measures relative scratch hardness. (Diamond is ten, and the hardest steel is eight.)
The back of the case has a thread so that it can be screwed into the case.
Where the crown is threaded and tightens to the case by screwing the crown into a matching threaded tube that is part of the case. The crown has a gasket that is compressed & seals the opening when the crown is tightened – thus ensuring water resistance. A Screw-Down Crown is an essential feature for any watch you intend on swimming with. An additional benefit of the Screw-Down Crown is that the crown is somewhat more protected from accidental knocks. See Winding Crown, Crown
Second Time Zone Indicator Aka “GMT” or Dual Time Zone”
An additional dial that can be set to the time in another time zone. This allows the wearer to know the time in two zones simultaneously. See GMT Time, Dual Time, World Time.
The watch mainspring is wound by a device inside the watch that rotates with normal wrist motion.
Rotating the winding and setting crown to bring the watch's hands to the correct time.
A resilient bearing that takes up the shocks received by the watch’s balance staff and protects its pivots from damage.
A watch’s ability to withstand an impact equal to being dropped onto a wooden floor from a height of 3 feet.
The actual amount of time it takes for the earth to rotate around a fixed star once per day. The time interval between two consecutive transits of the same star over the same meridian is used for measurement. A Sidereal Day is approximately 3 hours and 56 seconds longer than a solar day.
Primarily utilized in observatories for astronomical research. It is the interval between two successive meridian transits of a fixed star.
The Salon International de la Haute Horlogerie (S.I.H.H.) is a trade show held each year in Geneva. New model watches are unveiled for the trade and the show is not open to the public.
Case, dial, and various parts of the movement have been removed to reveal the watch's primary components. The watch features a crystal on both the front and back.
Slide Rule aka Navigation Computer
A device consisting of a scale on the outer edge of a watch face which enables mathematical calculations such as fuel consumption, climbing times & converting miles into nautical miles or kilometers.
Small Seconds Dial
The seconds are displayed by a hand in a small subsidiary dial and not from the center of the timepiece.
The time it takes the earth to rotate once a day using the sun as a reference. The time between two sun transits over the same meridian is measured.
Solar Powered Batteries
Batteries in a quartz watch that are recharged via solar panels on the watch face.
The time of day based on the position of the sun. Use of a sundial to measure solar time is one example.
A variation of a minute repeater that sounds the time automatically every hour (petite sonnerie) or quarter hour (grande sonnerie).
Split Seconds Chronograph Aka “Rattrapante”
A chronograph with two center seconds hands; the extra hand runs concurrently with the main hand but can be stopped and made to catch up. "Split Seconds hand" refers to a flyback (Rattrapante) hand and a regular chronograph hand. The flyback hand can be stopped while the chronograph hand continues to time laps or multiple finishing times. This divides the hand. The split-seconds allow recording the times of events that start at the same time
A spring-loaded metal bar mounted between the case lugs (horns) that is used to attach a strap or bracelet.
Each of the four sides of a square-shaped watch case are the same length.
A durable metal alloy that is almost rust resistant and rarely corrodes or discolors and, therefore, is highly suitable for watch case and bracelets. It is sometimes used on the case backs of watches made of other metals.
The time that is kept locally in each of the time zones when it is not daylight savings time.
The shaft that connects to the movement’s winding mechanism. The crown is fitted on the opposite end.
Refers to manually winding a mechanical watch using the winding crown and stem.
The part of a quartz analogue movement that moves the gear train and in turn moves the watch’s hands.
Sterling silver is a highly reflective precious metal, which is 92.5% pure and is often used in watches & watch dials.
A strip or band of leather or rubber that holds the watch to the wrist. It must be non-metal to be considered a strap; a metal version is referred to as a bracelet.
A smaller sub-dial on the main dial that displays seconds at a constant rate.
A small sub-dial on a watch face used for purposes such as indicating the date, power reserve or keeping track of elapsed time.
Sweep Seconds Hand
A second hand that is mounted in the center of the dial, instead of a sub-dial, and “sweeps” the entire dial of the watch.
A watch can only be labeled Swiss-Made if the manufacturer started, adjusted, and controlled the assembly work in Switzerland. A minimum of 50% of the movement's components must be made in Switzerland. Case and bracelet cannot be made in Switzerland; they must be delivered unassembled and assembled there.
A certificate of origin – a mark that identifies that a watch has been assembled in Switzerland and has components of Swiss origin.
Tachymeter Scale aka Tachometer
A common characteristic of chronograph watches. Determines the velocity over a predetermined distance. The chronograph is activated upon passing the starting point and deactivated upon passing the finish line. The tachometer scale displays the speed in units per hour to the wearer. Typically, the scale is engraved on the bezel or printed on the dial's outer diameter.
A tang buckle is a traditional Loop & Pin (belt type) buckle.
A rectangular watch with bars along the sides of its face. It was inspired by the tracks of tank used in World War II and designed by Louis Cartier.
Pure tantalum is a lustrous, silvery, and soft metal. It is nearly resistant to chemical attack at temperatures below 150 degrees Celsius. Due to an oxide film on its surface, tantalum is essentially corrosion-proof.
A watch or stopwatch used to measure the distance traveled by an object over a given period of time. It is typically a timer or chronograph with a graduated dial or bezel that computes the speed of an object in kilometers or miles per hour.
Earth's rotation on its axis is measured in time units.
The twenty-four regions or divisions of the globe that define time zones. The time zone indicator for Minnesota will be either Chicago or Mexico City.
A device, such as a clock or watch, used to measure time.
A device for registering intervals of time without any indication of the time of day.
A metal that appears slightly darker/grayer than stainless steel. Titanium is lighter and more durable than steel. Titanium is increasingly used in watchmaking, particularly for sports and diver watches due to its resistance to corrosion in saltwater.
The accuracy rating of a watch's movement, expressed in seconds per day. The most stringent guarantees are reserved for chronometers, with the majority of watchmakers guaranteeing some level of tolerance.
A tongue, or tang, is a movable metal piece in a buckle which penetrates the holes in a leather strap.
A watch shaped like a barrel with two convex sides.
A mechanism that keeps track of and displays elapsed time, often on a subsidiary dial.
The Tourbillon compensates for differences in rate resulting from a watch's various positions. Mounting the balance and escapement in a rotating cage is the guiding principle. The balance and escapement rotate around their common axis through all positions to average out errors. Tourbillon cages or platforms typically rotate once per minute, but there are also four-minute and six-minute tourbillons. The Tourbillon complication is an incredibly difficult feat to achieve and typically commands a premium price.
The center, third, fourth, and escape wheels in a watch or clock. Mainspring band and balance assembly aren't train parts.
A slightly radioactive substance used to allow the hands or hour markers of a clock to glow in the dark. Radiation levels are so low that they pose no health risk. Tritium-containing watches must be marked with the letter T near 6 o'clock on the dial.
Triple Date/Triple Calendar
A type of calendar that shows the day, date, and month.
Uni-Directional Rotating Bezel
See bi-directional rotating bezel
U.T.C. (Coordinated Universal Time)
The official measurement of time across the globe, independent of all time zones.
Up And Down Indicator
A smaller sub-dial on a watch dial or a separate indicator that displays the amount by which the mainspring has been wound up or down. Typically, dials and indicators display "up and down." Down is the wound zero position. Maximum wound position is "up."
Vibration Per Hour or VPH
This refers to the movement of an oscillating element that is limited by two extreme positions. The balance of a mechanical watch usually vibrates at a rate of five or six a second, more commonly recognized by (but not limited to) 36,000 28,800 or 18,000 vph.
One vibration in a watch movement with a balance wheel is one swing. A semi-oscillation is a vibration. A vibration or semi-oscillation occurs when the balance wheel swings in either direction, for example clockwise or counterclockwise. This is expressed in Hertz (Hz) or vibrations per hour (vph), which is also known as A/h. The number of oscillations per second is the frequency. Double hertz to get vibrations per second. Multiply that number by 3600 to get vph. Modern mechanical watch movements run at 4 Hz, or 28,800 vph. A 4Hz watch makes 4 oscillations or 8 semi-oscillations per second. 480 semi-oscillations (or vibrations) per minute (60 seconds). 480 vpm x 60 min = 28,800 vph. In a 28,800 vph watch, a chronograph can time events to the nearest 1/8 of a second. Using this formula, a 2.5 Hz or 18,000 vph watch can time events to the nearest 1/5 second. 3 Hz or 21,600 vph gives 1/6 second accuracy. 36,000 vph or 5 Hz watches can time to 1/10 second.
For years, watchmakers made luxury timepieces from solid gold. As time passed, new metals swept the watch world. Steel, titanium, platinum, and ceramic timepieces have joined 18k gold as options for luxury watches.
The capability of a watch case to withstand complete submersion in water. Some waterproof watches are also designed to withstand high water pressures, as required for scuba diving watches.
A water-resistant watch can withstand some water. Check the watch manual for water resistance. Most watches are water-resistant. The watch's water-resistance rating is given when it's new and tested in ideal conditions. Seals and gaskets deteriorate as a watch ages, lowering its ratings. So the water resistance must be tested annually.
White gold is real gold mixed with white metals like nickel and zinc to form a durable alloy. It was originally developed as a replacement for platinum (a rare and expensive naturally white metal). The alloy contains around 75% pure gold and is therefore good enough for everyday use.
Also referred to as a pinion, the wheel is a circular part that revolves around an axis to transmit power.
Also called the Going Train. The series of wheels and pinions that transmit power from the mainspring to the escapement while, at the same time, driving the minutes and seconds hands (the hour hand is driven by the watch’s motion works). The first wheel in the wheel train is the mainspring barrel. The others are known as the center wheel, third wheel, fourth wheel and escape wheel. Each has an accompanying pinion that drives the next wheel in the train.
This is the action of tightening the mainspring of a watch. It can be done manually, by means of the crown, or automatically, via a rotor which is made to swing by the movement of the wearer’s wrist.
Winding Stem aka Winding Crown
The grooved button on the outside of the case, used for setting the hands of the watch & the day and date of where applicable. It is also used for winding the mainspring of a mechanical watch. It is also known as the crown.
World Time Complication
A dial that displays 24 time zones. The dial lists cities. The scale next to the city where the hour hand points indicates the zone's hour. The minutes are read as usual. The dial is usually found on the watch's outer edge. World Timer watches have this function.
A wristwatch designed to be worn with a band or bracelet.
Yacht-Timer is a type of wristwatch used to time boat races.
Yellow gold – or simply, gold – is a precious metal that occurs naturally. It’s a very soft metal and in its purest form, it bends easily out of shape. That’s why gold used in jewelry needs to be mixed with harder alloy metals. These help to make the gold more durable and keep its shape.