Watch Glossary

Analog Display	An analog watch displays the time using hands and a dial
Automatic Watch	An automatic or self-winding watch requires no battery and is instead powered by the movement of your wrist. As you wear the watch and create natural motion, the mainspring inside the movement is wound by the balance wheel which in turn moves the gears to power the functions on the dial.
Bezel	The bezel is the top ring around the face of the watch which holds the glass and the case together. Some bezels are designed to equip the timepiece with additional functions like a tachymeter scale for measuring speed or a 60 minute scale which is essential for divers when measuring a length of a dive.
Bi-Directional Rotating Bezel	A bezel that can be rotated either clockwise or anticlockwise.
Calendar	A feature on a watch dial that displays the date and often the day of the week and month. Calendar functions are commonly displayed through small apertures or 'windows' on the dial.
Calibre	A watch's calibre refers to the mechanism or movement inside the watch. You can have quartz, mechanical, automatic or self-winding calibres.
Case	A case of a watch is the primary housing for the internal watch movement.
Case back	The case back is simply the back of the watch. Some case backs are closed so you cannot see inside the watch whereas others are known as exhibition case backs which allow you to see the workings of the movement inside.
Chronograph	A chronograph is variety of watch equipped with several functions that allow you to measure elapsed time, almost like a stop watch on the wrist. Chronographs come in many different styles, with some watches having two or three sub dials.
Chronometer	A chronometer is a watch that has been tested and certified to meet specific precision standards by an official testing institute. Any Swiss watch certified as a chronometer must have an accuracy of +6 and -4 seconds per day.
Complication	Something referred to as a complication is known as an additional function on a watch other than the basic timekeeping functions of hours, minutes, and seconds. A date window, GMT hand or power reserve indicator are examples of additional complications.
COSC	COSC stands for the Controle Officiel Suisse des Chronometres or the Swiss Official Chronometer Testing Institute. This institute is responsible for certifying the official chronometer status of a watch. If a watch is COSC certified then it must have an accuracy of +6 and -4 seconds per day.
Crown	The crown is a small knob most commonly found on the right hand side of the case. The crown is better known for adjusting functions on the dial such as the time and date. In self-winding watches, the crown is also used to wind up the movement.
Crystal	The crystal of a watch is the transparent glass used to protect the dial. The crystals can either be made from resin, minerals or sapphires.
Date Window	A small aperture on the dial where the date is displayed.
Deployment Buckle	A deployment buckle or folding buckle is a type of clasp on a watch's strap that folds into itself for additional safety and ease of use.
Dial	The dial is the face of the watch which displays the time and other complications.
Digital Display	Rather than displaying the time with hands on a dial, a digital display shows the time with numbers.
Diving Watch	A diving watch is a timepiece with at least 200 metre water resistance, a unidirectional bezel and a screw-down crown and case back. All these functions allow the watch to remain protected from the damages of underwater diving.
DLC (Diamond Like Carbon)	DLC (Diamond Like Carbon) is a type of metal coating with a grey/black finish. DLC is similar to PVD coating but considered even more scratch and corrosion resistant.
Escapement	The escapement is a device found in mechanical watches which converts rotational energy into lateral impulses. The tick-tock sound you hear in watches is evidence of the escapement at work. .
End of Battery Life Indicator (EOL)	The EOL indicates when it is time to replace the existing battery. Different manufacturers use different methods to indicate a low battery. One example is if a second hand usually sweeps, when the battery is low it will begin to tick.
Finishing	The finishing of watch is the effect used on the case metal. For example a stainless steel case can have a polished finish, brushed finish or gold plated finish.
Fly-Back Hand or Retrograde Hand	A retrograde hand is found only on a half circle or arc shaped sub-dial. This is because instead of the hand following a circular design, it must jump or 'fly' back to the beginning. For example if you have a retrograde date function, the hand will jump back to 1 after reaching the last day of the month.
Geneva Stripes	A form of decoration found on components of a watch's movement.
Grand Complication	A grand complication is considered one of the most complex achievements of haute horlogeries since it is a watch with a huge range of complicated functions. It is widely agreed that a watch has a grand complication if it has a minute repeater, moon phase, perpetual calendar, split-seconds chronograph and a grand and petite sonnerie.
Horological	The art of making a timepiece.
Incabloc Shock Protection System	An incabloc shock protection system is used in most mechanical watches to help protect the critical alignment of components such as the hairspring and balance wheel in the event of an unexpected physical shock.
Jewel	In mechanical watches, jewels are used to reduce friction in the movement since they wear very slowly. Synthetic rubies and sapphires are examples of some of the jewels used. It is considered that the more jewels a movement has, the higher grade the watch is.
Lugs	Lugs are projected from the watch case and hold the strap and case together.
Luminous	If something is luminous or has luminous coating, then it will glow in the dark. Many watches have luminous hour markers or hands that allow you to tell the time when there is insufficient light.
Mechanical Movement	Rather than being powered by a battery, a mechanical watch is powered by several tiny components that must be wound up. There are two types of mechanical movements available: automatic winding and manual winding.
Manual Winding Movement	Unlike an automatic movement which is powered by the movement of your wrist, a manual winding movement must be wound manually by twisting the crown and charging the mainspring.
Mineral Crystal Glass	A type of watch crystal used to protect the dial made from heated hardened glass. Although still highly scratch resistant, sapphire crystal glass is superior in its durability.
Moon Phase	Moon phase is a type of complication which displays the current phase of the moon as you would see it in the sky.
Movement	A watch's movement refers to the internal mechanism that powers all its functions. There are two main types of movements: quartz and mechanical (including automatic and manual-winding).
Perpetual Calendar	A complication which accurately displays the date, day, month and year at the same time. Perpetual calendars also have the ability to take into account a leap year without any need of adjustment from the wearer.
Pin Buckle	The traditional style of clasp on a watch strap, similar to that of a belt buckle. A pin buckle involves inserting a small pin through a hole in the strap to fasten and secure.
Power Reserve Indicator	All mechanical watches have a limited power reserve, for example once fully wound a watch will have so many hours before it needs winding again. Thus, a power reserve indicator is a complication that displays how much power remains.
PVD (Physical Vapour Deposition)	PVD or Physical Vapour Deposition is a type of coating which combines ions and gas to create a thin layer of plating. PVD coating is extremely thin but it enables a colour to be applied to steel while also increasing its resistance to wear.
Quartz	This is a watch with a battery-powered mechanism. Unlike mechanical movements, quartz movements need replacing ever 2-3 years.
Rotor	In automatic winding mechanisms, the rotor is responsible for winding the mainspring which then powers the watch. The rotor is an unbalanced, semicircular piece of metal often seen through exhibition case backs which turn freely in both directions as your move your wrist.
Sapphire Crystal	Sapphire crystal glass is a synthetic crystal used on most luxury watches to protect the dial. It is second only to diamond in its hardness making it extremely durable and scratch resistant.
Screw-down Crown	A crown that screws in and out of the case. Screw-down crowns increase a watch's water resistance and help prevent dust from entering the internal mechanism.
Smartwatch	A smartwatch is like a wearable computer commonly linked to your smartphone. Smartwatches are often equipped with touchscreen display, fitness apps, notification alerts and heart rate monitors.
Skeleton Watch	A skeleton watch is a mechanical timepiece where some or all of the moving parts of the calibre are visible. Skeletonised watches display components of the movement through the dial or the case back.
Sub-dial	A sub-dial is a small dial placed on the inside of the main dial to display an additional complication.
Superluminova	Superluminova is a type of luminous substance used on watch hands, markers and indices. The luminous substance allows these elements to glow in the dark and is recharged by natural or artificial light.
Water Resistant	A watch's water resistance refers to how waterproof it is to different pressures.
Tachometer (Tachymeter)	A watch with a tachymeter function can be used to measure speed. Tachymeter scales are usually found on the bezel and used in conjunction with chronograph complications.
Tourbillon	A tourbillon is a complex type of complication used to improve the balance of the watch and help eliminate accuracy errors caused by gravity and other forces. This is done by mounting the escapement and balance wheel in a rotating cage to contradict any effects of gravity. Tourbillon complications are usually only found in high quality and more expensive watches.
Unidirectional Bezel	A bezel that can only be rotated clockwise, used most commonly in diving watches.