Annual Calendar
A watch displaying the day, date, and month that automatically makes allowances for the different lengths of the months in the calendar module of a watch.  An annual calendar requires only a single manual correction per year from the end of February to the 1st of March.

Altimeter
A function that provides altitude by responding to changes in barometric pressure, commonly found in pilot watches.

Aperture (or dial window)
A small opening in a watch dial most commonly used to display the date, In some cases the aperture will display the hour, or day of the week.

Appliqué
The numerals or symbols attached to the dial of the watch.

Automatic (or Self-winding)
This term refers to a watch with a mechanical movement (as opposed to a quartz or electrical movement). The watch is wound by the motion of the wearer's arm rather than through turning the winding stem. A rotor that turns in response to motion winds the watch's mainspring. If an automatic watch is not worn for a day or two, it will wind down and need to be wound by hand to get it started again. An English watchmaker by the name John Harwood successfully adapted this system in 1923.

Arbor
An arbor is the shaft, or axle that a gear rides on.

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. To synchronize your watch with atomic standard time, call (303) 499-7111

Atmosphere
Used as a measure of the water tightness of watch case, one atmosphere equals average air pressure at sea level, approximately 14.7 pounds per square inch. One atmosphere equals 33.90 feet of water, so a 3 ATM water resistant watch is considered water resistant to approximately 100 feet. However, watches should never be worn while diving or swimming unless they are a divers watch which has been inspected for water resistance by a watchmaker.

Baguette
Ladies style watch with a thin, elongated rectangular or oval face.

Bangle Bracelet
A type of bracelet found on some ladies watches that are of fixed size.

Balance Wheel

The Balance Wheel controls accuracy.  If you look inside a watch, you will see how busily this little wheel works.  Turning alternately in each direction, it swings the jeweled lever once every 1/5th of a second.  Its balance is tested at rest and in motion -- and the final adjustment is so delicate that the smallest weight change in ONE of the tine timing screws around the rim of the wheel may upset its balance. Now commonly made of Invar, a special steel resistant to changes in dimension due to fluctuations of heat or humidity, and usually is mounted with a hairspring also of Invar or a similar alloy.

Balance-cock
A separate bridge holding the balance and regulator assemblies.

Balance Spring
Also referred to as the "Hair Spring", this spring controls the swing of the balance.

Barrel
Often called the "mainspring barrel", a wheel featuring a toothed disc on one face. The toothed rim of the barrel drives the train.

Beat
Measured in either Beats per hour (BPH) or Beats per second (BPS), this is the number of times per hour or second that the balance wheel goes through a full arc of motion in either direction. The usual number of Beats per hour is 18,000.

Bezel
The “bezel” refers to the ring around the crystal that is seen when looking directly at the face of the watch. On many luxury watches, the bezel contains diamonds or gemstones while on sportier model watches the bezel may contain calibrated markings for timing events. The bezels on the sport watches can turn in one direction, or occasionally, in either direction.

Bolt, or slide
An operating part, on repeater watches, made of the same metal as the case and shifted along the caseband with the fingernail. The repeating-slide winds the spring of the striking mechanism.

Bottom plate
A metal plate bearing the bridges and various parts of the movement.

Bridge (or bar, or cock)
A metal movement part that is attached to a bottom plate and holds at least one bearing of a rotating part.

Bridge 
An additional plate fixed on the main plate by pins or screws.

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

Cabochon Crown
A rounded semi-precious stone or synthetic material usually black, fitted into the watch crown as an ornament.

Calibre
In simple terms, it means "diameter". In watchmaking, the term refers to the specific layout and shape of a movement and the bridges, and its various components as well as the designer of the movement.

Caliber (UK)
Several related words in different European languages make the meaning of this word somewhat confused. In Swiss usage "Kaliber or Calibre" means the model type, such as Cal. 48, meaning "model 48". United Kingdom usage, calibre carries the meaning of the layout of a watch movement, or less often, its size. In America, this word is not used at all, and applies only to firearms.

Calendar Watch
A watch with a mechanism that shows the date, or on more complex watches, the month, day, moonphase and even the year. Most calendar watches have to be adjusted manually at the end of the month, but the mechanism of a perpetual calendar watch, adjusts itself automatically.

Carillon
Striking mechanism, or chime, that involves two or more bells of varying tones.

Central piece
Central part of the watch-case, which houses the movement.

CENTER (Centre) SECONDS (UK/USA) :
Also called sweep seconds (USA). The second hand is mounted in the center of the dial for greater visability and ease in reading. Second hands are also mounted at the 6:00 position, and more rarely at other positions on the dial.

Case
The container housing the movement of the watch and protecting it against dust, moisture, jarring and other hazards. Usually consisting of the caseband, the bezel, and the caseback.

Caseback
The bottom of the watchcase that can be opened for access to the watch movement.

Caseband
The watchcase edge between the bezel and caseback. Also called the middle.

Chamfer (or bevel)
To take down a sharp angle into a flat edge which often produces a luminous strip along the contours of the chamfered part or area. Hand chamfering results in particularly clean recessed and protruding angles.

Chronograph
A watch able to measure elapsed time, that can be reset to zero at will which also functions as a regular watch. A stop watch or timer is different, in that they only function to measure elapsed time. Both chronographs and stop watches have similar mechanisms that enable the second hand, and other hands that record elapsed time to be reset to zero.

Chronometer (Swiss: Chronometre)
Several different definitions exist for chronometer. The most common present meaning is a highly accurate wrist watch or pocket watch with official certification of its accuracy. "Chronometer" also applies to highly accurate ships clocks, which are also officially certified, but now usually know as "marine chronometers". However, historically, marine chronometers used for determining latitude which were equipped with a chronometer escapement instead of a lever escapement is the strict definition of the term.

Clasp
The fastener or catch used to open and close a watch bracelet. Also see Deployant Clasp.

Circular Graining
A surface decoration of slightly overlapping concentric circles, often found on the bridges and base of watch movements and even occasionally on dials.

Column Wheel
The castle shaped wheel in a chronograph that acts as a cam to operate the various levers causing the chronograph mechanism to be set in motion. Chronographs with a column wheel are considered by many watchmakers to be superior to those without them due to the sureness of their action.

Complications
Supplementary time mechanisms, with the exception of the display of hours, minutes and seconds, that are added to a basic movement. Complications belong to three main categories: those that provide extra time indications; those that strike or chime the time of day; and those that provide a variety of astronomical indications. "Grand Complication" watches feature mechanisms from all three above categories.

"Côtes de Genève"
The term means "Geneva ribbing" which are regular, parallel strokes that impart a ribbed aspect to the surface of given parts, often the bars and bridges of a movement.
Knurled or grooved knob located on the outside of a watch case and used to manually wind the watch.

Crown
The button used to manually wind and set the time of a watch.

Crystal
The transparent cover on a watch face made of glass crystal, synthetic sapphire or plastic. Better watches often have a sapphire crystal which is highly resistant to scratching or shattering.

Deployant Clasp
A clasp mechanism for use with watch straps. This allows a leather or other watch strap to operate similar to a watch bracelet. This gives a nicer, more finished appearance than the traditional tang-type buckle on most straps.

Dial
Disc or plate made of metal or another substance, inscribed with various markings, including obvious indications for the hours, minutes and seconds. Uniquely varied in shape, decoration and material, they are inscribed with numerals, figures, symbols, divisions and other information.

Dial Window
See Aperture.

Ebauche
A French term for a movement blank, which is an incomplete watch movement before its assembly is completed, and comprises the main plate, the bridges, the train, the winding and setting mechanism and the regulator. Not part of the ebauche is the timing system, the escapement and the mainspring.

Elinvar
Also know as Invar and under several other brand names this special alloy was invented by Dr.Charles Guillame (France) for which he received the Nobel Prize for chemistry. This alloy is non-magnetic, non-rusting, and the reacts little if at all to changes in temperature. Closely related to it are Beryllium alloys with the same properties, but more flexible. The advent of these metals revolutionized watch technology at the end of World War One, and made possible the modern watch.

Escapement



The most important part of the watch. This acts the same way as the governor on a steam engine acts and allows the power stored in the mainspring to be released through the gears in a regular and control manner . There are many types of escapements, but the only type of escapement used presently in mechanical wrist watches is the lever escapement. The lever escapement consist of three parts, a balance wheel, the lever and the escape wheel.

Escape Wheel
In a lever escapement, this is the last gear in the gear train, but it does not function to turn other gears. Instead it has specially shaped teeth that are alternately locked and unlock by the motion of the balance and lever to regulate the motion of the watch.

Etablissage
French term for the method of manufacturing watches and/or movements by assembling their various components. It generally includes the following operations: receipt, inspection and stocking of the "ébauche", the regulating elements and the other parts of the movement and of the make-up; assembling; springing and timing; fitting the dial and hands; casing; final inspection before packing and dispatching.

Etablisseur
French term for a watch factory which is engaged only in assembling watches, without itself producing the components, which it buys from specialist suppliers.

Equation of time
The amount of time used to compensate for difference between true solar time to the mean, or civil, solar time at any given time.

Factory, works
In the Swiss watch industry, the term "manufacture" means a factory in which watches are manufactured almost completely, as distinct from an "atelier de terminage", which is concerned only with assembling, timing, fitting the hands and casing.

Fast Beat Watch
A watch where the motion of the gear work, and consequently of the balance wheel is faster than the usual watch, which is 18,000 beats per hour. Fast beat watches run from 22,000 beats an hour on up.

Fly-back Hand, (retrograde date hand)
Usually, a hand indicating a date or time against a scale and then "flies back" to catch up with to another date or time. For example, a hand that "flies back" to the beginning of the month after reaching the 28th, 29th, 30th, or 31st day of the month.

Geneva Stripes
a type of ornamental engraving done on watch movements. Although the effect of broad lines on the watch movement is quite simple and attractive looking, it requires a highly trained engraver to do properly

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

G.M.T
abbreviation of Greenwich Mean Time. Time is calculated from the naval observatory at Greenwich, England, who is zero degrees longitude.

Guilloche
Ornamental engraving in the form of circular and interlocked lines, often found on watch dials, usually done mechanically. Also refereed to as engine turning.

Grand strike
("Grande sonnerie" in french) Mechanism that can automatically sound the hours and quarter hours and which repeat hours, quarters and minutes on demand.

Hairspring
Also referred to as the "Balance Spring", this spring controls the swing of the balance.

Horology
The science of time measurement, from Greek hora ‘point in time’ and logos ‘word, speech, process of reasoning’. Strictly speaking a horologist is an abstract researcher, not a practical constructor of timekeepers, although the two aspects have often overlapped in one person's achievement.

Horns
The parts on a wristwatch case, usually joined to the central piece, to which the straps are attached.

Incabloc
The best known of the various competing shock absorbers for watches, it is manufactured by Potescap SA and considered an industry standard.

Jewel
A pierced circular synthetic sapphire or ruby that is used as a bearing for watch gears. The top of the jewel has a depression to hold oil. Jewels are set in the metal plates that support the gears. The pivot (the tip of the gear arbor) goes though a hole in the jewel. Synthetic sapphires or rubies tend to retain oil much better than metal. Also, synthetic sapphires or rubies are far more friction free than metal bearings, so a fully jeweled movement is one of superior quality.

Jumping hours
On a watch dial, the digital numbers representing hours appearing through a small aperture or window.

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

Kif
A method of shock protection for a wristwatch movement, developed in the 1930's. Other named techniques for shock protection include Parachoc, Incabloc, Unisafe and Novochoc. Kif is the shock protection system used several watch makers, including Rolex. See also 'Incabloc' above.

Lesser strike
("Petite sonnerie" in french)Striking-mechanism setting limited to the automatic strike of hours

Lever
Any pivoting element and anchor-shaped part made of steel or brass that is part of the escapement.

Lever Escapement
Invented by Thomas Mudge (England) in 1759, it eventually came to displace all other types of watch escapements, and remains the only type of escapement being presently manufactured for watches. It consists of an escape wheel, the "lever" itself and a balance wheel. The lever, when acted on by the balance wheel, locks and unlocks the escape wheel, allowing power to flow through the gear train in a uniform motion.

Ligne
A pre-metric system of measurement still used in Switzerland to measure watch movements. A "ligne" is 1/12 of a royal French inch, which was abolished in 1798, but persisted in the watch industry. Movements 8 3/4 lignes and up are considered suitable for use in men's watches, and movements 8 3/4 lignes and smaller are for use in women's watches.

Lugs
The four protrusions on a typical watch case used to attach a bracelet or strap.

Mainspring
The principal spring of a watch that supplies the force of motion to the gear trains.

Manufacture
In the Swiss watch industry, this French term names companies where the watch manufacturer produces in-house all the major parts and components of a watch. Opposite from a "manufactory" which is to an "assembler" who merely puts together movements from parts acquired elsewhere, times and adjusts the movements, and fits on the hands and cases them up.

Minute Repeater 
A special complication found on a few very high end mechanical watches and some more affordable quartz watches. On the major quarters of the hour, or when activated by the wearer, the watch chimes the current time. The minute-repeater chiming pattern uses a mid-note for each hour, followed by a high-mid note pair for each quarter hour, and if chiming a time between the quarters, adds a high-note for each minute past the quarter hour. So a time like 2:22 would chime as: "dong, dong, ding-dong, ding, ding, ding, ding, ding, ding, ding."

Mirror polish
Extremely meticulous and elaborate polishing operation resulting in a flawlessly bright and smooth surface, absolutely free from scratches and blemishes.

Moon Phase
A type of dial showing the changes in the moon's phases (rising, full or waning moon). A lunar month is roughly 29 1/2 days, so it is made to rotate in this period. In former times, this was a very useful accessory showing what nights would be moon lit, an important consideration before the era of street lights, when high tide and low tide would be, and it was also useful in fishing and agriculture. To this day it is still favored among some fishermen.

Movement
The assembly making up the principal elements and mechanisms of a watch or clock: the winding and setting mechanism, the mainspring, the train, the escapement, and the regulating elements.

NOS or New Old Stock
items that are older but still technically considered new as they have never been used or sold to a customer. Often these are unsold watches, watch bracelets or other parts that have been in a store's inventory or warehouse for a long time--often for years or decades after that model has been discontinued by the manufacturer.

Pallet
Part of the lever escapement. Typically, it is in the shape of a ship's anchor.  Steel or brass part of watch that controls the small rotation of a ratchet wheel.

Perpetual calendar
A complication displaying the day of the week, the date, the month - also correcting for leap years - and the phases of the moon. Operating on the 400 year cycle, perpetual calendars require no manual correction before February 2100.Perpetual calendars are almost always self winding and, if worn constantly, are one of the most useful of all complications.

Plate
The portion of the movement which supports the bridges and other plates.

Pivot
The reduced or turned down part of an arbor. This part commonly projects through the hole in watch jewels.

Power Reserve
A measure of the amount of time a watch will run after being fully powered or wound, with no additional power input. Normally, this means when a mechanical watch is fully wound or a quartz watch has a brand new battery. Many modern mechanical watches have a power reserve of 40 hours. Power reserve also applies to battery-less quartz watches, which may have power reserves from 40 hours to 6 months. On battery-operated quartz watches, the term is sometimes used to refer to the expected battery life--typically 12 to 32 months.

Racks
The striking mechanism incorporates three round-shaped parts called racks: one for the hours, one for the quarters and one for the minutes.

Regulator
A mechanism inside watches which can be used to speed them up or slow them down and bring the watch to more exact timing.

Repeater
A watch mechanism that sounds hours, quarters or minutes or repeats them on request. First designed to help the wearer to tell the time in the dark, they were always the most complex of watches and were the most difficult to miniaturize to fit into a wristwatch. See Minute Repeater.

Rotor
In automatic winding mechanisms, an unbalanced, semicircular metal turns freely in both directions winding the mainspring.

Ruby
A synthetically made precious stone used to reduce friction and wear in a movement.

Sapphire Crystal
Scratch-resistant man-made material (synthetic corundum) used for watch crystals, fitted over the dial and sometimes set into the case back.

Self Winding
Another name for automatic watches.  See Automatic Watches.

Shock Absorber
A system whereby the jewels that support the balance staff, one of the most delicate parts of a watch ,are mounted in spring loaded settings that absorb shock if the watch should be jolted or dropped. Shock absorbers are among the most important parts of the watch, as they protect the most vital parts from damage.

Skeleton
Watch in which the case and various parts of the movement are cut away to reveal the watch's mechanical elements.

Slide(-bolt)
Found on the case middle and operated with a fingernail, the slide triggers or locks a function or mechanism. The repeater slide also serves to wind the striking mechanism.

Split-seconds chronograph
A chronograph mechanism controlling two second hands, one called the split-seconds hand, superimposed on one another.

Stamp, swage
A precision tool that has stamps and presses components of a movement, through shaping, bending, blanking and cutting them.

Tachymetre
The divisions on a dial that allow the conversion of a single event into the relative number of events per hour.

Tourbillon
A regulating device that cancels the effects of gravitation on the precision of a watch movement by rotating the balance, lever and escapement around a single axis. The mechanism that even in its most conventional version, is extremely hard to manufacture.
Invented in the 1790s by Abram-Louis Bruguet (France) this has become the Holy Grail of watchmaking despite the fact that it has no practical utility. Breguet invented this device to overcome the problem of position error, but this problem may be sufficiently cope with by adjustment of the balance spring. In this device, the entire escapement is fit onto a carriage which revolves every 60 seconds. The construction of a tourbillon is highly difficult and is, in of its self proof of the highest skills in watchmaking.

Tonneau Watch
Describing the shape of a watch case that looks like a barrel with tow bulging sides.

Ligne
A pre-metric system of measurement still used in Switzerland to measure watch movements. A "ligne" is 1/12 of a royal French inch, which was abolished in 1798, but persisted in the watch industry. Movements 8 3/4 lignes and up are considered suitable for use in men's watches, and movements 8 3/4 lignes and smaller are for use in women's watches.

Train
A set of wheels and pinions in a watch movement.

Vibration
Describes the movement of a pendulum or other oscillating element, limited by two consecutive extreme positions. The balance of a mechanical watch making five or six vibrations per second vibrates at 18,000 or 21,600 times per hour.

Waterproof
The commonly used term is now "water resistant", because it is very hard to say that a watch is indeed permanently "water proof". Various types of seals are used to assure that the case is water resistant, and the watch crown must also be a screw down type with appropriate seals. To assure water resistance, the watch should be tested once a year to be sure that all seals are intact and functioning properly.

Watch Winder
A powered device that rotates an automatic watch to keep it wound and running when not on the wrist.

Water Resistant
Describes a watch case designed to prevent water from entering.

Winding System
Shaft on which the crown is fixed on an end.