Watch Glossary

A watch complication that shows at minimum the day, date and month, often the year as well. Compare with perpetual calendar.

A watch that isn't affected by magnetic fields. Magnets can affect a watch's time by interfering with the mechanisms. Everyday objects like the clasps on handbags and iPad cases, TVs, fridges and cars can cause enough magnetism to damage the watch. By using materials that can't be magnetised, like silicon, within the movements, the watch can be classed as antimagnetic.

This is a thin film applied onto the crystal of a watch to reduce reflection and therefore increase visibility. It can be applied to both the outside and inside of the crystal.

A small window or opening in the dial that displays information such as the day or date.

The numbers on the dial marking each hour. Arabic numerals are in 1, 2, 3, 4, 5, 6, 7, 8 and 9 form.

An atomic calendar takes into account various lengths in months as well as leap years.

An automatic watch movement is a type of mechanical movement. First introduced during the beginning of the 20th century, this movement winds itself while worn on the wrist so it doesn't need daily hand-winding. An automatic watch that isn't worn for a couple days (depending on how much power reserve it has) will need to be manually wound again to get started. Read more about automatic watch movements.

The balance spring is a very thin spring that coils and recoils causing the balance to swing back and forth at a constant rate - which in turn moves the watch's gears.

The balance wheel is the beating heart of any mechanical watch. It's a weighted wheel that oscillates back and forth to divide time into equal segments.

The mainspring is encased in the barrel. The size of the barrel determines the length of the power reserve for the watch.

These are markers on the dial to signify the hour. Baton hour markers are in an elongated rectangular shape.

A battery powers a quartz watch.

The bezel is the ring surrounding the dial of your watch, sometimes adorned with a tachymeter scale to measure speed or distance. The bezel can be made from various materials such as ceramic, stainless steel or gold.

This is a type of bezel that can be rotated in two directions; both clockwise and counter-clockwise. It can be used to make mathematical calculations or keeping track of elapsed time. The other type of bezel is a unidirectional rotating bezel.

This is most commonly a metal strap securing the watch to the wrist. A bracelet can be resized by removing or adding links.

The bridge is a plate or bar that is mounted to the mainplate, forming the frame of the movement and holding the rotating gears.

This is the fastening fitted to leather straps so the watch stays secure and comfortable on your wrist.

A cabochon is a gem that has been polished but not faceted so it's smooth and round. Purely decorative, they are found on the dials, crowns and sometimes bezels of watches.

This is a complication that shows the date, often the day and year as well.

The calibre, or calibre, is the specific style or size of the watch movement. Brands often name their movements with specific model names; this is the calibre.

Otherwise known as domed crystal, this is where the crystal covering the dial has been arched to create a domed appearance. It is also more impact resistance than a flat crystal.

This is the main body of the watch, where the movement is housed and the dial sits. Cases can come in many different shapes, sizes and materials to give a watch its own style.

This is the underside of the watch that lies against the skin. Some are made of crystal so you can see the movement inside.

This is a stopwatch function, giving you the ability to accurately measure time. This is usually operated by two pushers on the crown, one which stops and rests the stopwatch and the other which starts it.

For a watch to be called a chronometer, it must have passed rigorous testing by the C.O.S.C (Controle Officiel Suisse des Chronometeres or Official Swiss Chronometer Testing Institute). A highly coveted and renowned certificate, the test measures the performance of a watch at three various temperatures and five different positions for fifteen consecutive days.

A complication is an additional watch feature other than timekeeping. Simple complications include chronographs, alarms and calendars whilst more advanced complications include slide rules, tourbillons and perpetual calendars.

The C.O.S.C is the Controle Officiel Suisse des Chronometre - the only official chronometer testing organisation in Switzerland.

This function allows the wearer to determine how much of a preset time has elapsed.

This is the button or knob on the outside of the watch case which controls and sets some of the functions. It is used to wind the mainspring in mechanical watches, and you can set the time and calendar with it. See also: screw-down crown.

The crystal is the transparent cover protecting the watch dial. This can be made from glass, plastic or sapphire and can come with coatings such as anti-reflective. The crystal can also be domed or cambered.

This is a feature on the dial that shows the day of the week and/or the date of the month.

This is a tri-folding and expandable clasp that secures the two ends of the watch strap or bracelet, so you can easily put the watch on your wrist, set the correct size and then close it.

The dial is the face of the watch that shows the time, using various markers and indicators. You can have a digital dial, an analogue dial or a combination of both.

A digital dial shows the time through a digital numerical display instead of with a dial and hands (an analogue display).

A dual time watch measures your local time as well as at least one other time zone, often shown through an extra hand or sub dial.

Also known as cambered crystal, this is where the crystal covering the dial is arched and domed.

A very important watch part, the escapement is a mechanism within mechanical movements that transfers the energy into the impulse action - or the timekeeping element. The escapement controls the rate at which the balance wheel and watch hands rotate.

Otherwise known as the dial, the watch face is where the time is shown using various markers and indicators.

The gear train is a system of gears that transfers the power from the mainspring to the escapement.

GMT or Greenwich Mean Time is also known as UTC (Universal Time Coordinated) or Zulu Time. It's the international standard time, and every time zone in the world is referenced against GMT. A GMT watch is a timepiece with a 24 hour format hand that indicates a second time zone.

Guilloche is an engraving process in which intricate patterns are etched into the materials on a watch.

Shown on an analogue dial, the watch hands rotate around the dial and point at the hour markers so you can tell the time.

A hand-winding mechanical movement is one which needs to be wound regularly for accurate timekeeping. By winding the crown, this causes mainspring to wind up and release the energy to power the watch.

Also known as the balance spring, the hairspring is a very fine spring that causes the recoil of the balance wheel.

Haute horlogerie is translated to high art of watchmaking. It is used to describe the renewed tradition of high-class mechanical watches. To maintain the tradition of Haute Horlogerie, the Fondation de la Haute Horlogerie was founded in 2005.

A helium escape valve is a function found on some professional diving watches. When diving to depths of 200m and beyond, divers use a diving bell which contains a high proportion of helium. Helium atoms are extremely small and slip inside a watch case, and as the watch depressurises on the ascent to the surface, the build-up of helium atoms inside the case can cause the crystal to pop off. The purpose of a helium escape valve is to allow the gas to escape safely.

This is the study and science of time, which includes studying time, timepieces and the art of watch craftsmanship.

Similar to hour markers, indices are a line or indicator on the watch dial to indicate the hour. They are used instead of numerals.

A jewel in the watch world usually refers to synthetic gemstones, usually made of ruby or sapphires that serve as a bearing for the gear trains to reduce friction and ensure the accurate timekeeping is upheld.

This is a chronograph function that breaks up the time segments or laps of a race. At the end of a lap, the timer resets to zero so the following lap can be timed.

This is a small forked lever that sits in between the escape wheel and the balance wheel. It divides into two pallets that lock and unlock the escape wheel as the lever is flicked back and forth by a jewel on the balance, moving the hands forward at a steady rate.

These are the part of the watch case that the bracelet or strap attaches to.

This is a coating on watch numerals, hands and other detailing on the dial to make them glow in darkened environments. See also Superluminova.

The base or plate on which all the parts of a mechanical watch movement are mounted.

Housed inside the barrel, the mainspring is a spiral spring which is the source of power in mechanical watches. Wound by hand or by an oscillating weight, the force of the spring unwinding powers the watch.

A manual or hand-winding mechanical movement is one which needs to be wound regularly for accurate timekeeping. By winding the crown, this causes mainspring to wind up and release the energy to power the watch.

Often shortened to just 'manufacture', this French term refers to a watch company that designs and manufactures at least one of its movements entirely in-house.

A mechanical movement is one which uses a mechanism to measure time. Powered by a main spring, it has lots of different components and parts to make it work. There are two types of mechanical movements; automatic (self-winding) and manual (hand-winding).

This is an indicator on the dial that displays what phase the moon is in.

The heart of the watch, the movement is what powers the watch. It can either be mechanical or quartz.

A watch complication that displays the day, date and month, but requires less adjustment than an annual calendar as it automatically adjusts for a leap year.

The length of time that a mechanical movement can run without being rewound. I.e. how much power remains in a watch's mainspring.

A display on the dial that shows how much power reserve a watch has left.

A button on a chronograph watch that starts, stops and/or resets the chronograph function.

A quartz watch is a battery powered watch. Powered by an electronic movement with a tiny quartz crystal, which oscillates at near perfect frequency - making quartz watches incredibly accurate.

A rattrapante, or split-seconds, chronograph has two seconds hands, meaning it can time multiple events simultaneously.

Reserve de marche is the French term for power reserve indicator.

A rotating bezel allows divers to work out how long they've been underwater for. Before a dive, you would align the 12 o'clock bezel marker with the minute hand, allowing the elapsed time, up to 60 minutes, to be read on the bezel.

One of the many components within an automatic mechanical movement, the rotor is a weight that swings back and forth when the wearer moves his arm, which in turn winds the mainspring to provide the power.

Used to protect the dial or as a transparent caseback, sapphire crystal glass is highly scratch resistant and the glass type that is the least prone to shatter.

Often found on dive watches, a screw down crown seals the crown to the case of the watch to ensure no water gets in.

This is a complication that shows a different time zone.

An automatic watch movement is a type of mechanical movement. First introduced during the beginning of the 20th century, this movement winds itself while worn on the wrist so it doesn't need daily hand-winding. An automatic watch that isn't worn for a couple days (depending on how much power reserve it has) will need to be manually wound again to get started. Read more about automatic watch movements.

Similar to an exhibition case back, a skeleton dial shows off the inner workings of the watch through a partially cut-out or transparent dial.

This is a device on the outer edge of the watch face used to do mathematical calculations. It consists of two scales, one marked on a rotating bezel and one on a stationary scale. The rotating scale can be slid against the stationary scale to make calculations.

A solar powered watch is powered entirely or partly by a solar cell, taking charge from most light sources.

A split seconds chronograph is another name for a rattrapante chronograph.

This is the sprung steel pin that holds the strap to the case.

This is another term for chronograph. It's a function on a watch that gives you the ability to accurately measure time.

The watch strap secures the watch to the wrist, usually made out of leather, rubber or fabric.

This is a secondary dial on the main dial used to display purposes and functions.

This is the brand name for the coating that is placed onto watch numerals and hands to illuminate them in darkened environments.

A tachymeter scale measures the speed travelled over a measured distance, often found on the bezel of a watch.

Often found on diving watches, the bezel can only rotate in one direction rather than both. This is so it can't accidentally be rotated in the wrong direction and cause divers to miscalculate how long they have left under water before the air supply runs out.

Watches that are water resistant can withstand some amount of water and still work. Water resistancy varies between watches. Check out our guide to water resistancy here.