Welcome to the Watch Glossary

Our Watch Glossary for the ultimate watch nerd.

Our aim, with the launch of the watch and timepiece glossary, is to collect all the most commonly used or heard terms, in watchmaking, in one single place. This column will allow you to get familiar with words like power reserve, barrel, escapement, or summarize what a complication, whether it is a tourbillon or a perpetual calendar, actually means. Also, we introduce the meaning of certifications, from the longstanding COSC certificate to the most recent ones like the Master Chronometer certification, adopted by Omega on its timepieces. The glossary is not a static section since watchmaking evolves; instead, it is unstoppably updated as new terms and technologies keep enriching the world of watches.

Analog display.

A watch that displays the time by using hands and a dial.


It is one of the parts that belong to the escapement. It has slightly different shapes depending on the type of escapement. Its name comes from a ship anchor-like design.


Watch capable of withstanding magnetic fields. There are different ranges of magnetic resistance, from a few Gauss up to fully antimagnetic resistance, something only OMEGA Watches can currently guarantee on its Master Chronometer certified watches.


Resilient bearing in a watch that is intended to protect the balance staff from accidental shocks.


It is a cylindrical metal box closed by a cover, that contains a spiral spring called the mainspring, which provides energy to run the timepiece.

Balance wheel.

A part of a mechanical watch that oscillates, dividing time into equal portions.


The bezel is particularly useful on diving watches, allowing you to check dive times. In this case (as it is in the case with a chronograph equipped with a tachymeter scale) it is rotatable and comes in two parts, a metal (or ceramic, depending on the type of watch) ring, paired to a graduated ring ( it can be in aluminum or ceramic, in the past it was also in bakelite).

Big Date.

Two overlapping discs, one showing the numbers from 0 to 3 and the other the numbers from 0 to 9, rotate in opposite directions, thus displaying a double-digit number indicating the date.


A feature that shows the day of the month, and also the day of the week, in some cases. Some calendar watches show the date on sub-dials while others display the date via a scale printed on an outer ring, placed into the dial.


Also known as calibre, the caliber is the type of a watch movement encased in an assigned timepiece. Its name is usually an association of the manufacturer's name and a standard code, e.g: ETA 2824.


It is a composite material based on carbon fibre. Layers of carbon fiber are placed on each others and united under controlled pressure and temperature using a PEEK (Polyether Ether Ketone) based binder matrix. Carbotech™ has been patented by Panerai.


Crafted in one or more parts, it is the container that encases the mechanical movement. It comes as a single piece, as with some professional diving watches or unconventional materials, such as ceramic or carbon fiber composites.

Case back.

Indicates the back of the watch: it can be screwed-in, pressure-fastened, or secured to the case via screws. Occasionally, it also comes as a single-piece with the case on specific professional diving watches (for example, some SEIKO Prospex). It can be closed or see-through, thanks to the adoption of a plastic or sapphire glass that allows the wearer to admire the movement.


Widely used for the crafting of a watch case and, in recent years, also for the bezels of diving watches and dials. Obtained from zirconia powder (ZrO2), ceramic offers superior scratch resistance, paired to reduced impact resistance (resilience) in comparison to metals. The design and assembly of a ceramic case are key to guaranteeing the right mechanical and shock resistance.


Ceratanium™ is an alloy developed and patented by IWC that aims at combining the scratch-proofness of ceramics with the mechanical resistance of titanium. It is adopted by the IWC Pilot's Watch Double Chronograph Top Gun Ceratanium.


It is a small lens applied to the crystal that protects the dial, that helps magnify the date.

Complete calendar.

In a complete calendar, the date, day, and month are displayed. Since the disc of the month has 31 days, those having a 30-month length, and February, require manual correction.


It is the addition of any mechanical complication to a movement that usually displays the time.

Counter (or Register).

The counter is an additional register placed on the dial, which provides further information compared to traditional ones. For example, the thirty minutes counter on a chronograph's dial.


A button, fluted or not, placed on the case side used to wind the mainspring in mechanical watches. It is also used to set the time, when pulled out, and for setting a watch calendar. A screw-down crown is adopted to increase water resistance and protect the movement from dust.


The corrector is a tiny button, placed on the case side, that allows the wearer you to update the date on watches with a calendar.


It is the acronym for Controle Officiel Suisse des Chronomètres, the Swiss organization that releases the Chronometer Certificate. A Chronometer certified watch has undergone several tests under assigned conditions and meets precise running precision requirements. A watch certified as a Chronometer carries the wording "Chronometer" on the dial.

Côtes de Genéve.

A regular wave pattern obtained by engine-turning and polishing on a movement's parts or a dial too (take a Mido watch as an example).


Rolex's patented luminescent material deposited on indexes and hands in order to help read the time in the dark.


It is a device used by watch repairers and service centers to reveal any discrepancy between current and expected running precision, thus helping a watchmaker adjusting a timepiece.


It allows the wearer to measure intervals of time without affecting the normal time-telling function of the watch.


An instrument for measuring time very accurately. For any watch to be called a chronometer, it must meet the standards set by the C.O.S.C. (Controle Officiel Suisse des Chronometres).


It indicates the date of the month. There are different types of a date display: via a window, or a pointer, where an additional hand usually placed in a separate counter displays the date of the current month. Requires manual correction to manage the transition from month to month.


A watch that indicates the day of the week as well as the date.

Deployant buckle.

A buckle that fastens to the watch strap or bracelet, and opens and fastens using hinged extenders. Invented by Louis Cartier in 1910.


In tuning fork based watches, time measurement is based on the regular oscillation of a tuning fork, controlled by an electronic circuit. It was invented by the Swiss electronic engineer Max Hetzel, in 1952, while he was working at Bulova.

Digital watch.

A timepiece that shows the time through a numerical display instead of via a dial and hands.

Diver's watch.

It is a term that identifies a specific category of watches suited for professional diving.


An acronym for Diamon Like Carbon, it is a surface treatment based on carbon microparticles which are deposited on steel using a chemical deposition process. The D.L.C. treatment gives the watch a dark look and increases protection from chemical and corrosive products, and in areas of higher friction such as close to the rotating bezel. Also, it is a hypoallergenic treatment.


The French term for water proof.


Swiss manufacturer of mechanical and quartz movements owned by the Swatch Group.


It is the number of oscillations of the regulating organ. It is divided into hours, in mechanical watches, in second in quartz ones.


It is the acronym for Greenwich Mean Time and identifies a complication capable of displaying two or more time zones on the dial by usually coupling a 24-hour rotating bezel with day and night indication through a two-color rotating bezel, paired to an additional hand. There are, however, different types of watches with GMT complication.


Surface decoration or pattern. An even pattern is cut, usually on the dial.


Indicates the most common system for protecting a timepiece's movement from accidental shocks.


It is the measurement unit that identifies the size of a movement. According to this measurement system, one line corresponds to 2,255mm.


Luminescence refers to emitting rays of light. A luminescent material is applied to numbers, indexes and hands in order to read the time in the dark or under dim light. The most renowned manufacturer of luminescent material, in the industry, is Super-Luminova®; vertically integrated watch manufacturers like ROLEX and SEIKO use proprietary materials like Cromalight and Lumibrite respectively.


A micro-rotor is a tiny winding rotor placed inside the movement to reduce its thickness; it is the most refined technical solution when a brand aims at designing an automatic mechanical timepiece with reduced case thickness. The best example so far is the Bulgari Octo Finissimo Automatic.


It is an additional part of the base movement, through which one or more complications can be added.

Perpetual Calendar.

The perpetual calendar is a calendar complication that adjusts the watch’s calendar for the varying length of months and leap years too. This cycle will end in 2100, and the wearer should apply the first manual correction.

Rattrappante (or Split Seconds Chronograph, or Double Chronograph).

A Split Seconds Chronograph is a watch that has two hands (in an analog display), one of which can be stopped via an additional push-button to display an intermediate time while the other hand continues to run.

Power Reserve.

A feature of a mechanical watch that displays, on the dial or the case-back, the remaining power in a watch movement, showing the length of time until the timepiece will need to be wound again.


Part of an automatic watch that winds the mainspring by constantly rotating. It comes in various geometries, sizes, and materials, depending on the winding capability, movement design, and value of the watch. An ultra-thin automatic timepiece, for instance, adopts a micro-rotor or a peripheral winding rotor.


The shaft that connects to the movement’s winding mechanism. The crown is fitted on the opposite end.


A strip or band of leather or rubber that secures the watch to the wearer's wrist. It must be non-metal to be regarded as a strap; it is otherwise a bracelet.

Swiss Made.

A timepiece can be considered to be Swiss made if its movement is Swiss, its movement is cased up in Switzerland and the manufacturer carries out the final inspection in Switzerland.

Time equation.

It is a complication that displays the difference in minutes between calendar time and real-time. The Breguet Marine Equation Marchante 5887, for example, adopts a Time Equation complication.

Time zone.

Time zones refer to the twenty-four regions of the globe. Our time zone here in Italy will be indicated by either Milan, Rome or Naples.

Tonneau watch.

A tonneau watch is a timepiece whose shape looks like a barrel, whose sides are convex.

Tourbillon Cage.

It is the rotating cage that includes the tourbillon and the balance wheel, anchor and escapement wheel.

Water Resistant.

A watch is water resistant when it is capable of resist splashes of water. This will indicate the depth that a watch can be worn underwater.


It is a timepiece that displays the 24 time zones of the main cities of the world; on premium luxury watches, like those produced by a Saxon watchmaker, Glashütte Original, it displays all the current time zones (35 are) available.


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