Watch Terms & Glossary

You can find a detailed Glossary of Watch terminology and wording.

Acrylic Crystal – Sometimes referred to as Hesolite or Hesalite, an acrylic crystal is basically plastic. Polymethylacrylate is often used. Benefits of an acrylic crystal are that is flexes rather than shatters on impact, it doesn’t produce too much glare under bright light and it can be polished easily

Alarm Watch – A watch provided with a movement capable of releasing an acoustic sound at the time set. A second crown is dedicated to the winding, setting and release of the striking-work; an additional center hand indicates the time set. The section of the movement dedicated to the alarm device is made up by a series of wheels linked with the barrel, an escapement and a hammer striking a gong or bell. Works much like a normal alarm clock.

Altimeter – This 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.

Amplitude –Maximum angle by which a balance or pendulum swings from its rest position.

Analog or Analogue – A watch with a dials, hands, and numbers or markers that display a twelve -hour time period.

Analogue Digital – A dual display digital and a conventional analogue watch.

Analog QuartzThe most commonly-used term in referring to any analog timepiece that operates on a battery or on solar power and is regulated by a quartz crystal.

Anchor Escapement – the regulator that controls the speed of a mechanical movement.

AntiMagnetic – Mechanical movements can be influenced by the magnetic fields often found in common everyday places. This problem is generally countered by using anti- or nonmagnetic components in the movement as in the eta 2824-2. If the parts most affected by a magnetic field (balance, balance spring and escapement) are made of non-magnetic materials the watch is called anti-magnetic. Bomb squad experts require this type of watch. As used in the Bell & Ross Type Deminuer and Christopher Ward Malvern Automatic

Antireflection, Antireflective – A film created by steaming the crystal to eliminate light reflection and improve legibility. This film can scratch quite easily so it is common in exceptional pieces to use this treatment on the inside of the crystal glass although some brands such as Dubey and Schaldenbrand are unusual in that they prefer to coat both sides of all their wristwatches.

Aperture – An opening in the dial that displays certain information such as date, day, month, or moon phase or even the movement

Applique – Numerals, images or symbols cut out and stuck to dial.

Atmosphere (ATM) – The 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) indicates water-resistance.

Atomic Time Standard Provided by the U.S. National Institute of Standards and Technology, Time and Frequency Division, Boulder, Colorado, atomic time is measured through vibrations of atoms in a metal isotope that resembles mercury. The result is extremely accurate time that can be measured on instruments. Radio waves transmit this exact time throughout North America and some “atomic” watches can receive them and correct to the exact time.

Automatic Movement – Self-winding watch whose movement is mechanical. A fly wheel (the rotor) turns by the motion of your arm and winds the mainspring. The stored energy in a spring is turned into mechanical energy that creates the watch movement. These watches can be shaken or in most cases manually wound if the power reserve is depleted.

Automatic Winding – A rotating weight, set into motion by moving the wrist, winds the spring barrel via the gear train of a mechanical watch movement. Automatic winding was invented during the pocket watch era in 1770 by Abraham-Louis Perrelet, who created a watch with a weight swinging back and forth (a pocket watch usually makes vertical movements). The first automatic –winding wristwatches, invented by John Harwood in the 1920’s, utilised hammer winding, whereby a weight swung in an arc between two banking pins. The breakthrough automatic winding movement via rotor began with the ball bearing Eterna-Matic in the late 1940’s, and the technology hasn’t changed fundamentally since then. The Eterna-Matic is the predecessor of the well known ETA Movements currently  owned by The Swatch Group.

Auto Repeat Timer – Function that counts down time and then resets itself as soon as a preset time has elapsed. It repeats the countdown continuously until a button is pressed to stop the function.

BaguetteLadies style watch with a thin, elongated face; usually rectangular in shape but may be oval.

Balance – Mechanical watches are regulated with the balance and balance spring. The mainspring provides energy. The hairspring, coupled to the balance, makes it swing to and fro, dividing into equal parts. Each to and fro of the balance is called oscillation. One oscillation equals 2 vibrations.

Balance Spring – A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulates the timekeeping. This is also known as the hairspring. Component of the regulating unit that, together with the balance, determines the movement’s precision.

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 or CockA metal plate fastened to the base plate at one point, leaving room for a gear wheel or pinion. The balance is usually attached to a bar called the balance cock.

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 controlled energy.

Base Metal – Any non-precious metal.

Battery – Device that converts chemical energy into electricity. Most watch batteries are silver oxide type delivering 1.5 volts. Much longer-lasting lithium batteries are 3 volt.

Battery Life – The minimum period of time that a battery will continue to provide power to run the watch. Life begins at the point of manufacture when the factory initially installs the battery.

Battery Reserve Indicator – Some battery-operated watches have a feature that indicates when the battery is approaching the end of its life. This is often indicated by the second hand moving in two second intervals instead of each second.

Bearing – Part on which a pivot turns, in watches it is represented mostly by jewels.

Beat –  The number of times per second (Beats per Second) 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.

Bevelling –Chamfering of edges of levers, bridges and other elements of a movement by 45º, a treatment typically found in high-grade movements

Bezel – The circle around the top of the crystal. Mostly used to 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, counter clockwise, or both to assist in calculations.

Bi-Directional Bezel – A bezel that both clockwise and counter clockwise.

Blued Screw – Swiss watch making tradition dictates that a movement should contain blued screws for aesthetic reasons. Polished steel screws are heated, or tempered, to relax the steel, turning it a deep blue colour in the process.

Bracelet – A metal band attached to the case. It is called integral if there is no apparent discontinuity between case and bracelet and the profile of attachments is similar to the first link.

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 the functions such as the chronograph or the fly back.

Cabochon – Any kind of precious stone, such as sapphire, ruby or emerald, uncut and only polished, generally of a half-spherical shape, mainly used as an ornament of the winding crown or certain elements of the case

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.

Calendar, Perpetual – This is the most complex horology complication related to the calendar feature, as it indicates the date, day, month and leap year and does not need manual corrections until the year 2100 (when the leap year will be ignored).

Calibre – 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 or bezel.

Cannon – An element in the shape of a hollow cylinder, sometimes also called pipe or bush, for instance the pipe of the hour wheel bearing the hour hand.

Carat (Karat) – Unit of gold fineness (and gemstone weight). Pure gold is 24k. 18k gold is 75% pure.

Carousel –Device similar to the tourbillon, but with the carriage not driven by the fourth wheel, but by the third wheel.

Carriage or Tourbillon Carriage –Rotating frame of a tourbillon device, carrying the balance and escapement. This structural element is essential for a perfect balance of the whole system and its stability, in spite of its reduced weight. As today’s tourbillon carriages make a rotation per minute, errors of rate in the vertical position are eliminated. Because of the widespread use of transparent dials, carriages became elements of aesthetic attractiveness.

Case – Container housing and protecting the movement, usually made up of three parts: middle, bezel, and back.

Center Second Hand –A sweep second hand, i.e. a second hand mounted on the center of the main dial.

Center-Wheel – The minute wheel in a going-train.

Ceramic – Used as a shield for spacecraft re-entering the earth’s atmosphere, high tech ceramic is polished with diamond dust to create a highly polished finish. Most popular found in black and white.

Champlevé – Hand-made treatment of the dial or case surface. The pattern is obtained by hollowing a metal sheet with a graver and subsequently filling the hollows with enamel. back to top

Chapter-Ring – Hour-circle, i.e. the hour numerals arranged on a dial.

Chime – Striking-work equipped with a set of bells that may be capable of playing a complete melody. A watch provided with such a feature is called chiming watch.

Chronograph – From the Greek words for time, chronos, and to write, graphein. Originally a chronograph literally inscribed the time elapsed on a piece of paper, with the help of a pencil attaché to a type of hand. We use the term today to describe watches that show not only the time of day, but also certain time intervals via independent hands that may be started or stopped at will as in the C4 Peregrine shown here. 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.  According to the Swiss law, a manufacture may put the word “chronometer” on a model only after each individual piece has passed a series of tests and obtained a running bulletin and a chronometer certificate by an acknowledged Swiss control authority, such as the COSC.

Circular Graining –Superficial decoration applied to bridges, rotors and pillar-plates in the shape of numerous slightly superposed small grains, obtained by using a plain cutter and abrasives. Also called Pearlage or Pearling.

Clasp – The attachment used to connect the two ends of the watch bracelet or strap around the wrist. Deployment Buckle – A three-folding enclosure, which 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. Hook Lock – Two separate units each fitting on either end of the bracelet which allows the watch to be laid out. One end of the closure hooks onto the other to secure the two ends of the bracelet. Jeweller’s Clasp – A closure that is generally used on better bracelets. Also allows it to lie flat. Sliding Clasp – Also a hook type method but allows for easy sizing of the bracelet by sliding up. Twist Lock – A closure similar to Jeweller’s Clasp used on ladies jewellery bracelets.

Cloisonne – A kind of enamel work – mainly used for the decoration of dials – in which the outlines of the drawing are formed by thin metal wires. The coloured enamel fills the hollows formed in this way. After oven firing, the surface is smoothed until the gold threads appear again.

Clous de Paris – Decoration of metal parts characterized by numerous small pyramids.

Colimaconnage – Decoration with a spiral pattern, mainly used on the barrel wheel or on big-sized full wheels.

Column-Wheel – Part of chronograph movements, governing the functions of various levers and parts of the chronograph operation, in the shape of a small-toothed steel cylinder. It is controlled by pushers through levers that hold and release it. It is a very precise and usually preferred type of chronograph operation.

Complication – Additional “function” added to a watch, such as a, stop watch, countdown timer, minute repeater, altimeter, asthometer, pulsometer, calendar, moon phase indicator, split second chronograph, power reserve indicator, alarm, etc.

Corrector – Pusher positioned on the case side that is normally actuated by a special tool for the quick setting of different indications, such as date, GMT, full or perpetual calendar.

C.O.S.C. – Abbreviation of 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”. A maximum gap of -4..+4 seconds per day is tolerated.

Cotes Circulaires – Decoration of rotors and bridges of movements, whose pattern consists of a series of concentric ribs.

Cotes de Geneve – Decoration applied mainly to high-quality movements, appearing as a series of parallel ribs, realized by repeated cuts of a cutter leaving thin stripes.

Countdown Timer – A function that lets the wearer keep track of how much of a pre-set period of time has elapsed. Some countdown timers sound a warning signal a few seconds before the time runs out. These are useful in events such as certain kinds of races.

Counter – Additional hand on a chronograph, indicating the time elapsed since the beginning of the measuring. On modern watches the second counter is placed at the center, while minute and hour counters have off-center hands in special zones, also called subdials.

Crown – The grooved button on the outside of the case, used for setting the hands on a watch, and the day and date, where applicable. It is also used for winding the mainspring of a mechanical watch. The crown is also known as a winder or winding stem, the interface used to wind a mechanical watch and to set the time and/or calendar of a watch.

Crystal – The clean cover over the watch face. Three types of crystals are commonly found in watches: acrylic crystal, mineral crystal and sapphire crystal.

Cyclops – A lens on the glass/crystal to magnify the date.

Decorated Movement – Some watch movements come highly decorated, for example with Geneva Stripes and blued screws. Whilst decoration may not improve function, it often indicates a degree of hand assembly/finishing and an attention to detail in the construction of a watch. Some watches show off the decorated movement through the use of a display back

Deployment Clasp – Used to secure the bracelet or strap of a wristwatch, to the wrist. There are three basic types of clasps; fold-over clasp, jewelery clasp and butterfly-clasp (aka deploy ant/deployment buckle, hidden deployment/deployment buckle, hidden double-locking clasp).

Deployment Buckle – This refers to two curved strips of hinged metal on a watch with a strap that fastens the strap tightly to the wrist. It tends to be a feature of quality watches and inhibits a watch falling from the wrist should it come undone.

Depth Alarm – An alarm set to sound when the wearer exceeds pre-set depth. The alarm stops when the diver ascends above pre-set depth.

Depth Meter or Depth Sensor – A device on a divers’ watch that determines the wearer’s depth by measuring water pressure. It shows the depth either by analogue hands and a scale on the watch face or through a digital display.

Deviation – A progressive natural change of a watch’s rate with respect to objective time. In case of a watch’s faster rate, the deviation is defined positive, in the opposite case negative.

Dial – Face of the watch that generally displays hours, minutes, and date etc.

Digital – Watch that uses an LCD or LED to display a continuous reading.

Display Back – A case back that is transparent (normally glass/sapphire crystal) so that movement may be viewed. (Also called: clear, see-through, skeleton, exhibition)

Divers Watch – Designed especially for divers whose lives depend on the reliability of their watch in the water. A watch that is water resistant to 200M. Has a unidirectional rotating bezel and a screw-on crown and back. Has a metal or rubber strap (not leather). May have a sapphire crystal and possibly, a wet-suit extension.

DLC (Diamond like Carbon) – A coating that produces a grey/black finish that is highly scratch resistant and corrosion resistant. This type of coating is like PVD, but even harder.

Dual Time Zone –  Tells the local time as well as time in another time zone. (Sometimes referred to as a GMT watch)

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

Eco-Drive – A name for a patented power mechanism found on some Citizen watches. This mechanism uses ordinary light to keep a rechargeable battery powered for watch operation. This technology is very sophisticated allowing some watch models to remain powered for up to 5 years in the dark. Watches with Eco-Drive technology will never need to have the battery replaced.

Elapsed Time Rotating Bezel – A graduated rotating bezel used to keep track of elapsed time. The bezel can be turned so the wearer can align the zero on the bezel with the watch’s seconds or minutes hand. After a period of time passes, you can read the elapsed time off the bezel. This saves you having to perform the subtraction that would be necessary if you used the watch’s regular dial.

Electroplating Process – Process of covering metal articles with a film of other metals. The article is immersed in a chemical solution; electric current (D.C.) flows through the solution from a piece of metal (anode) to the article (cathode), depositing metal thereon by electrolysis.

Endstone – Undrilled jewel, placed on the balance jewel with the tip of the balance-staff pivot resting against its flat surface, to reduce pivot friction. Sometimes used also for pallet staffs and escape wheels.

Engine-Turned – A surface decoration usually applied to the dial and the rotor using a grooving tool with a sharp tip, such as a rose engine, to cut an even pattern onto a level surface.

Equation of Time – Indication of the difference, expressed in minutes, between conventional mean time and real solar time. This difference varies from -16 to +16 seconds between one day and the other.

Equinox – The time when day and night are of equal length, when the sun is on the plane of the equator. Such times occur twice in a year: the vernal equinox on March 21st-22nd and the autumnal equinox on September 22nd-23rd.

Escapement – Is a mechanism made up of the escapement wheel, lever, and discharging roller, this acts to control the wheel movement and to provide pulses to pallets and thus the balance. It 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 its 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.

Exhibition Back – Same as a “skeleton” or “display” back.

Flange – Ring that the crystal sits on and separates it from the dial.

Fly-Back – Function that allows a chronograph to be reset to zero without having to stop the chronograph first.

Fold-Over ClaspHinged and jointed element, normally of the same material as the one used for the case. It allows easy fastening of the bracelet on the wrist. Often provided with a snap-in locking device, sometimes with an additional clip or push-piece.

Frequency – Number of vibrations a second or oscillations per second, in hertz (Hz) of a quartz watch. The number of vibrations per hour (VpH) of a mechanical watch.

Full Rotor – Automatic watches with rotors that travel 360 degrees in both directions.

Function – The same as a complication on a mechanical watch, but technically called a function on a quartz watch.

Gear Train – Made up of the going barrel, which drive the centre wheel. The centre 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 – The quality seal the displays the City of Geneva coat of arms. Watches must meet a least eleven strict criteria to be awarded the Geneva seal.

GMT – GMT, or Greenwich Mean Time, is based on the globe being divided into 24 time zones as established in the London Meridian Conference of 1884. The zero meridian runs through the Royal Observatory in the London suburb of Greenwich. In contemporary watch terminology, GMT is often used to describe a wristwatch that displays a second time zone or a 24hour indication.

GongHarmonic flattened bell in a steel alloy, generally positioned along the circumference of the movement and struck by hammers to indicate time by sounds. Size and thickness determine the resulting note and tone. In watches provided with minute-repeaters, there are often two gongs and the hammers strike one note to indicate hours, both notes together to indicate quarters and the other note for the remaining minutes. In more complex models, equipped also with en-passant sonnerie devices, there may be up to four gongs producing different notes and playing even simple melodies such as the chime of London’s Westminster Clock Tower or ‘Big Ben’ as it is commonly known.

Grand Complication – A Grand Complication is a combination of complications but it must have a perpetual calendar with or without moon phase indication), a split-second fly back chronograph and a minute repeater. Manufactures quite often include many other complications as well.

Guilloche – A surface decoration usually applied to the dial and the rotor using a grooving tool with a sharp tip, to cut an even pattern onto a level surface.

Hairspring – The (or balance spring) is attached to the balance and cock, and made of metal alloys. Its length determines the amount that the balance regularly oscillates: the shorter the spring the faster the watch runs. It returns the balance wheel back to a neutral position.

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 country of origin, the year of manufacture, the identity of the case’s maker, trademarks, reference numbers, and/or serial numbers.

Hammer – Steel or brass element used in movements provided with a repeater or alarm sonnerie. It strikes a gong or bell(s).

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 sometimes called a mechanical movement.

Helium Escape Valve – A helium escape valve is required for divers who spend a long time in hyperbaric chambers and breathe helium enriched gas. Helium molecules are much lighter than air and can therefore penetrate most watches. 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. The helium escape valve allows helium to escape without water entering the watch.

Hexalite – An artificial glass made of a plastic resin. Back in the 1960’s, many watches used either mineral glass or acrylic crystals. These are not difficult to scratch, but very inexpensive to replace. Now though, most all luxury watches use the highly scratch resistant synthetic sapphire crystals, there are some styles/brands that use the Hesalite (a name brand of fine acrylic crystal). The reason for this is directly related to the watch’s certification for use in space or in high stress/impact situations. While sapphire crystals are less prone to scratching, they can be shattered. When shattered, they break into tiny fragments that would be hazardous in some environments. So the Hesalite crystal is maintained on some specific models as a safety feature.

Horology – Science of time measurement, including the art of designing and constructing timepieces.

Incabloc – Incabloc is a shock-absorber system which help prevent damage from shocks to the balance pivots. Thanks to a retaining spring system, it assures an elastic play of both jewels, thus absorbing the movements of the balance-staff pivots when the watch receives strong shocks. The return to the previous position is due to the return effect of the spring. If such a system is lacking, the shock forces exert an impact on the balance-staff pivots, often causing bending or even breakage.

Index – Instead of a number, a marking indicating the hour and/or minutes.

Internal Bezel – A bezel inside the watchcase usually with a separate or additional crown.

Jewels – In the mechanical watch and some quartz watches, jewels are used as bearings for those parts of the movement subject to constant motion. They are not valuable at all in the monetary sense but they are valuable in aiding the precise running of a watch over a long period and reducing wear. It is a fallacy that the more jewels the better the watch. A basic hand wound mechanical usually comprises 17 jewels, which in the main is the optimum count. Automatics may require more for the winding mechanism itself. To minimise friction , the hardened steel tips of a movement’s rotating gear wheels (called pinions) are lodged in synthetic rubies (fashioned as polished stones with a hole) and lubricated with a very thin layer of special oil. These synthetic rubies are produced in exactly the same way as sapphire crystal using the same material.

Jumping Hour – A display in which the hour, shown through an aperture, instantly changes every 60 minutes.

Kinetic – Refers to the Seiko line of Kinetic watches. This innovative technology has a quartz movement that does not use a battery. Movement of the 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. Of course, if the watch is worn every day the capacitor is continually recharged. The watch alerts the owner to a low capacitor charge when the seconds hand starts to move in two second intervals. Some of Seiko’s Kinetic Watches have See-Thru CaseBacks, that use a clear, Hardlex crystal watch back to enable the wearer to view the kinetic movement.

Kinetic Auto Relay – A Seiko Kinetic Auto Relay watch is powered by human movement, however when it senses inactivity for three days, it puts itself into suspended animation to conserve energy. It can be re-activated with a few shakes of the wrist. It automatically resets itself to the exact time after to up to four years of dormancy.

Lap Timer – A chronograph function that times segments of a race. At the end of a lap a push button stops the time and then returns to zero to time the next lap.

Leap-Year Cycle – Leap or bissextile years have 366 days and occur every 4 years (with some exceptions, Calendar, Gregorian). Some watches display this datum.

Line – Ancient French measuring unit maintained in horology to indicate the diameter of a movement. A line equals 2.255mm. Lines are not divided into decimals; therefore, to indicate measurements inferior to the unit, fractions are used.

Liquid Crystal Display or LCD – A digital watch display that shows the time electronically by means of a liquid held in a thin layer between two transparent plates. All LCD watches have quartz movements.
Lubrication – To reduce friction caused by the running of wheels and other parts. There are points to be lubricated with specific low-density oils such as the pivots turning inside jewels, the sliding areas between levers, and the spring inside the barrel which requires special grease, as well as numerous other parts of a movement.

Lug – (same as horn) Part of case where bracelet or strap is attached.

Luminous Paint – Self-illuminating paint that is put on the hands and markers to read the time in low light situations. Super Luminova is the most popular type of luminous paint.

M – Indicating the depth of water resistance (200m) shown on the back of a watch case -see meter

Main Plate – The base plate on which all other parts of a watch movement are mounted.

Main Spring – The driving flat-coiled spring of a watch contained in the barrel, supplies power. The mainspring, located in the spring barrel, stores energy when tensioned and passes it on to the escapement via the gear train as the tension releases. Today, mainsprings are usually made of Nivaflex, an alloy invented by Swiss engineer Max Straumann in the early 1950’s. This alloy basically comprises of iron, nickel, chrome, cobalt and beryllium.

Manual Winding – A hand wound mechanical watch.

Manufacture – Most experts agree that the term, which is from Latin and means “made by hand”, should be used for a company that manufactures at least one calibre, or extremely important parts of it such as the base plate, on the premises. While ten years ago this constituted only a handful of companies in Switzerland and Germany today’s competitive market has forced a number of others to invest in developing their own movements. ETA is without doubt the largest.

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.

Meantime – The mean time of the meridian of the Greenwich Observatory, considered the universal meridian, is used as the standard of the civil time system, counted from midnight to midnight

Mechanical Movement –  Is 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.

Meter (M) – A measurement used to measure water resistance. (10m= 33.3ft= 1ATM= 1BAR)

Military Time or 24hr Time – When time is measured in 24-hour segments. To convert 12-hour time into 24-hour time, simply add 12 to any p.m. time. To convert 24-hour time into 12-hour time, subtract 12 from any time from 13 to 24.

Mineral Crystal or Mineral Glass – Watch crystal that has been tempered (heat treated) to increase its hardness and scratch resistance.

Minute Repeater – Mechanism indicating time by acoustic sounds. Contrary to the watches provided with en-passant sonnerie devices, that strike the number of hours automatically, repeaters work on demand by actuating a slide or pusher positioned on the case side. Repeaters are normally provided with two hammers and two gongs: one gong for the minutes and one for the hours. The quarters are obtained by the almost simultaneous strike of both hammers. The mechanism of the striking work is among the most complex complications

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. However, the difference of 0.03 days, i.e. 44 minutes each month, implies the need for a manual adjustment every two and a half years to recover one day lost with respect to the real state of moonphase. In some rare cases, the transmission ratio between the gears controlling the moonphase are calculated with extreme accuracy so as to require manual correction only once in 100 years.

Mother of Pearl – Iridescent, milky interior shell of the fresh water mollusc that is sliced thinly and used on watch dials. While most have a milky white lustre, mother-of-pearl also comes in other colours such as silvery grey, grey blue, pink, and salmon.

Movement – The entire mechanism of a watch. Movements are divided into two great families: quartz and mechanical; the latter are available with manual or automatic winding devices.

Nivarox – Trade name (from the producer’s name) of a steel alloy, resisting magnetization, used for modern self-compensating balance springs. The level of this material is indicated by the numeral following the name in decreasing value from 1 to 5.

Non Screw Locked Crown – Easier to set than a screw locked crown, but it is less water resistant.

Palladium – An Assayed and rare, lustrous metal that is 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. It has been recently classed as a precious metal by all the UK assay offices

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 – A toothed wheel usually made of steel with a small number of teeth.

Platinum – One of the rarest precious metals as well as one of the strongest and heaviest.

Pointer Calendar – Hands point to the date as opposed to appearing in an aperture.

Polished Finish – Brilliant meal surface obtained on the watchcase with a fine abrasive.

Power Reserve – In its purest sense, used to refer to how long a watch will run once fully wound. Thus a watch with a power reserve of 48 hours should run for that period. Often used to describe a watch, which has a power reserve indicator on the dial (usually a small pointer hand and a relevant scale).

Precision – Accuracy rate of a watch, a term difficult to define exactly. Usually, a precision watch is a chronometer of which accuracy-standard is certified by an official watch-rating bureau.

Pusher, Push-Piece or Push Button – Mechanical element mounted on a case for the control of specific functions. Generally, pushers are used in chronographs, but also with other functions.

PVD – Abbreviation of Physical Vapour Deposition a method of coating watch cases by integrating titanium particles and then depositing gold for colour. (Usually comes in black finish)

Quartz – A natural or synthetic silicon dioxide crystal used in quartz analogue 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. Timekeeping’s technical revolution found its way to the world’s wrists in the late 1960’s. This was principally a Swiss invention (the first working quartz watches were made by Girard-Perregaux and Piaget in a Swiss joint venture) but it was the Japanese firms, primarily Seiko, who were the first to see the advantages of the new technology and came to dominate the market. The quartz movement uses the famously stable vibration frequency of a quartz crystal subjected to the electronic tension (usually 32,868Hz) as its norm.

Quartz Movement – A movement powered by a quartz crystal. Quartz crystals are very accurate. They can be mass produced which makes them less expensive than most mechanical movements which require a higher degree craftsmanship.

Quick Set Date – Mechanism to set the date directly to avoid having to turn the hands over 24 hours.

Rattrapante – Used to describe the split seconds chronograph (see Fly back), which has two seconds hands sitting atop one another. On depression of a third chronograph button (most have two), the fly back hand will stop in order to measure say, a lap time; repressing this button with cause the fly back hand to fly back to the other seconds hand which has remained in motion. Addition of a second hand to measure split times. (Also called split-second chronograph.)

Regulating Unit – Made up by balance and balance spring, governing the division of time within the mechanical movement, assuring its regular running and accuracy. As the balance works like a pendulum, the balance spring’s function consists of its elastic return and start of a new oscillation. This combined action determines the frequency, i.e. the number of vibrations per hour, and affects the rotation speed of the different wheels. In fact the balance, by its oscillations, at every vibration (through the action of the pallets), frees a tooth of the escape wheel (see escapement). From this, motion is transmitted to the fourth wheel, which makes a revolution in one minute, to the third and then the centre wheel, the latter making a full rotation in one hour. However, everything is determined by the correct time interval of the oscillations of the balance.

Regulator – Regulating the functioning of a movement by lengthening and shortening the active section of the balance spring. It is positioned on the balance-bridge and encompasses the balance spring with its two pins near its fixing point on the bridge itself. By shifting the index, the pins also are moved and, by consequence, the portion of the balance spring capable of bringing the balance back is lengthened or shortened by its elastic force. The shorter it is, the more reactive it tends to be and the more rapidly it brings the balance back and makes the movement run faster. The contrary happens when the active portion of the balance spring is lengthened. Given today’s high frequencies of functioning, even slight index shifts entail daily variations of minutes. Recently, even more refined index-regulation systems were adopted (from eccentric to micrometer screws) to limit error margins to very few seconds per day.

Retrograde –Said of a hand that, instead of making a revolution of 360º before starting a new measurement, moves on an arc scale (generally of 90º to 180º and at the end of its trip comes back instantaneously. Normally, retrograde hands are used to indicate date, day or month in perpetual calendars, but there are also cases of retrograde hours, minutes or seconds. Unlike the case of the classical indication over 360º the retrograde system requires a special mechanism to be inserted into the basic movement.

Rotating Bezel – A bezel that can be turned. Different types of rotating bezels perform different time keeping and mathematical functions

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 win the mainspring.

Rubies – Ruby is a very hard stone now usually synthetic, which prevents the wear of gear train parts. Also called jewels.

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 aluminium oxide at very high temperatures. Chemically the same as natural sapphire, but colourless. It is hard and brittle so it shatters easier than plexiglass or mineral glass. 9 on a mohs scale, a diamond is 10. It is “grown” using a method invented by Auguste Victor Louis Verneuil in 1902 whereby a process that usually takes a thousand years to complete is accelerated to just a few hours, hence the use of the term synthetic. Unsurprisingly, sapphire crystal has become the material of choice to protect the dials of all high end modern wristwatches

Scale – Graduation on a measuring instrument, showing the divisions of a whole of values, especially on a dial, bezel. The scales mostly used in horology are related to the following measuring devices: tachometer (indicating the average speed), telemeter (indicating the distance of a simultaneously luminous and acoustic source, e.g. a cannon-shot or a thunder and related lightning), pulsometer (to calculate the total number of heart beats per minute by counting only a certain quantity of them). For all of these scales, measuring starts at the beginning of the event concerned and stops at its end; the reading refers directly to the chronograph second hand, without requiring further calculations.

Screw Down Crown –  Seals the crown against the case to prevent water penetration.

Screw Balance – Before the invention of the perfectly weighted balance by use of a smooth ring, balances were fitted with weighted screws to get the exact impetus desired. Today a screw balance is a subtle sign of quality in a movement due to its costly construction.

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. See also GMT and world time.

Sector – A circular sector, also known as a “pie piece” ,is the portion of a circle (or dial) enclosed by two radii.  

Self-Winding – A watch whose mechanical movement is wound automatically. A rotor makes short oscillations due to the movements of the wrist. Through a series of gears, oscillations transmit motion to the barrel, thus winding the mainspring progressively.

Shockproof or Shock-Resistant – Watches provided with shock-absorber systems (e.g. Incabloc) help prevent damage from shocks to the balance pivots. Thanks to a retaining spring system, it assures an elastic play of both jewels, thus absorbing the movements of the balance-staff pivots when the watch receives strong shocks. The return to the previous position is due to the return effect of the spring. If such a system is lacking, the shock forces exert an impact on the balance-staff pivots, often causing bending or even breakage

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.

Skeleton Watch – Visible movement through crystal on the front and back.

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)

Split-Second Chronograph – A split seconds chronograph or rattrap ante (catch up in French) or doppelchrono (double chrono is German) 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 – A very durable metal alloy consisting of steel, nickel, and composed mainly of chromium. It is virtually rustproof. It is also antimagnetic and used in most watch case manufacture.

Stem – The Axel that connects to the movement’s winding mechanism, the crown is normally fitted on 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 – Extra dials or registers.

Super-Luminova – A photo-luminescent non-radioactive material with a long period of phosphorescence. It reaches up to 100 times the brightness of Tritium. Tritium was the original, radioactive, substance used to coat hands, numerals and hour markers on watch dials to make reading the time in the dark possible.

Sweep Second Hand – Second hand that moves smoothly without starts and stops.

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

Tachymeter or 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 tachymeter. The average speed in 120mph. For example, the wearer could measure the time it takes a car to pass between two mile markers on a road. When the car passes the second marker, the second hand will be pointing to the car’s speed in miles per hour on the tachometric scale.

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.

Thermo-compensation – Quartz watches split time by exploiting the electromechanical phenomenon known as Piezoelectricity. When a continuous electrical current runs through it, the quartz crystal starts resonating at a constant frequency. Crystal oscillators for watches are manufactured to vibrate at 215Hz (32,768 Hz), a frequency that will then be halved 16 consecutive times by a processor to obtain the second (unit of time). The problem with quartz crystals is that they are easily affected by temperature: they tend to vibrate faster in heat and slower in cold. As a consequence, quartz watch can have between -10 to +15 sec. variations per month. Bearing in mind that mechanical watches can variate by -10 to + 15 sec. per day, the quartz oscillator is still far more accurate than the anchor escapement found in mechanical watches. The solution ETA engineers found was to add a thermometer that constantly feeds information to the processor, allowing it to compensate for errors caused by temperature. As a consequence, movements using this technology can be accurate to -10 to +15 sec. per year.

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 – Titanium is an environmentally friendly, natural metal that is 40% stronger and 30% lighter than stainless steel. It is hypoallergenic because it is nickel-free. It is perfect for water sport enthusiasts as it is extremely resistant to salt water and other forms of corrosion and able to withstand extreme temperatures. Many titanium watches are further enhanced with a glass coating for increased scratch resistance.

Titanium Carbide –  A black treatment, like DLC, it is very scratch resistant, and it is harder than PVD.

Tonneau – Particular shape of a watchcase, imitating the profile of a barrel, i.e. with straight, shorter, horizontal sides and curved, longer, vertical sides.

Tourbillon – A technically demanding device invented by Abraham Louis Breguet in 1801 to compensate for the interference of gravity on the balance of a pocket watch, thus improving its rate. In a tourbillon (from the French word for whirlwind), the entire escapement is mounted on an epicyclic train in a “cage” and rotated completely on its axis over regular periods of time, usually once a minute. This superb horological highlight, whilst being completely unnecessary for a wristwatch, is seen as a sign of technological know-how in the modern era.

Tritium – Slightly radioactive material that collects light energy and is used to coat hands, numerals, and hour markers on watch dials in order to make reading the time in the dark possible. Watches bearing tritium must be marked as such, with the letter T on the dial near 6 o’clock. It is gradually being replaced by nonradioactive materials such as Superluminova and Traser due to medical misgivings and expected governmental regulation of its use.

Two-Tone – A term use to indicate that a watch has both “silver” and “gold” tone colour which may or may not be genuine gold or silver.

Uni-Directional Bezel – An elapsed time rotating bezel, often found on divers’ watches, that moves only in a counter clockwise 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 moves in only one direction, the diver can err only on the side of safety when timing his dive. Many divers’ watches are ratcheted, so that they lock into place for greater safety.

Universal Time – The mean solar time of the Greenwich meridian, counted from noon to noon, Often confused with the mean time notion.

Variation – In horology the term is usually referred to the variation of the daily rate, i.e. the difference between two daily rates specified by a time interval.

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) the higher the number the smoother and more accurately the watch will run. (Same as BPH “beats per hour”)

Water Resistance – The ability of a watch to withstand water from entering the case. Water resistance is generally measured in four ways, where (1 ATM = 1 BAR = 10 METRES = 33.3 FEET). Usually measured in increments of one atmosphere (atm or bar, equal to 10 metres of water pressure) or metres and is often noted on the dial or case back. Swimming or snorkelling require 5 atm whilst scuba diving needs 20 atm to be sure. The record is held by The Hydromax by Bell & Ross which was developed for professional deep sea diving and is resistant to 11,100 metres!

Wheel – (or pinion) circular part revolving an axis to transmit power or motion. Centre wheel, front wheel, hour wheel, minute wheel, third wheel, transmission wheel.

Window – Aperture in the dial, that allows reading the underlying indication, mainly the date, but also indications concerning a second zone’s time or jumping hour.

World Time – Additional feature of watches provided with a GMT function, displaying the 24 time zones on the dial or bezel, each zone referenced by a city name, providing instantaneous reading of the time of any country.

Zone – Small additional dial or indicator that may be positioned, or placed off-centre on the main dial, used for the display of various functions (e.g. second counters).

Zodiac – Circular belt with the ecliptic in the middle containing the twelve constellations through which the sun seems to pass in the course of a year.