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Watch Glossary

Automatic Watch: An automatic watch requires no battery. The watch mainspring is wound automatically by a balance wheel which rotates due to normal wrist motion whilst wearing the watch. There are 2 types of automatic watches i.e. mechanical and automatic. Mechanical watches have to be wound up and automatic watches work on the movement of the wrist.
Bezel: This is the ring around the case which holds the crystal of a watch to the case of the watch.
Bi-Directional Rotating Bezel: A bezel that can be rotated either clockwise or anticlockwise.
Buckle: A traditional fastening on watches with material straps. A metal clasp through which the strap is passed and secured by a pin. Commonly referred to as a Pin & Buckle or Tang Buckle (a tang is a flattened pin).
Calendar: A feature that shows the date, and often the day of the week and month. Most calendar watches show the information digitally through an aperture on the watch face. If watches have perpetual calendars this will mean that the date will automatically change at the end of the month. Some chronograph watches show the information on sub-dials on the watch face.
Calibre: The mechanism inside the watch that tells the quality of the watch movement.
Case: A case of a watch is the primary housing for the internal watch movement.
Case back: The bottom of the watch case that can be opened for access to the watch movement for repair or battery change. Some watches have a sapphire glass case back which allows you to see the working mechanism of the watch.
Chronograph: This is a watch with a variety of extra features displayed on sub-dials. This can include hours, minutes, seconds, power reserve, date and moon phase.
Chronometer: This is a watch which has been measured for accuracy and tested for precision by an official testing institute.
Complication: An additional function other than basic timekeeping of the hours, minutes, and seconds. Certain features such as automatic winding or date are considered complications. The main complications are power reserve, moon phase, GMT, and full calendars. Great complications are split second chronographs, perpetual calendars, tourbillons, and minute repeaters.
COSC: This is the Swiss Official Chronometer Testing Institute that will certify the official chronometer status of a watch.
Crown: The 'Crown' is known better as the adjustment dial on the watch. The crown is used to adjust the time, date and for winding up the watch.
Crystal: The 'crystal' is the transparent cover over the dial. The crystals can either be made from resin, minerals or sapphires.
Date Window: A small opening in the dial through which the date is displayed.
Deployment Buckle: A buckle fastening featuring two strips of hinged metal which connect the two ends of a strap. When closed the strips fold underneath the watch strap locking it into place. When deployed the circumference of the strap is increased facilitating easy removal of the watch.
Dial: The 'dial' is the face of the watch showing the time.
Diving Watch: A watch that is at least 200m / 20 ATM water resistant. Has a one way rotating bezel and a screw-locked crown and back. Some watches have a helium escape valve to release the pressure after the diving
Electro-plating: A plating process which uses electrolysis to bond a thin, durable layer of a desired material to a metallic base layer. Commonly employed to layer gold, silver or chrome over a steel base, the resultant plating is measured in microns (one thousandth of a millimetre). Similar processes such as PVD (Physical Vapour Deposition) are used to bond non-metallic materials such as carbon to a steel base in order to create an extremely hardwearing surface layer.
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, i.e. if a second hand ticks, when the battery is low it will begin to jump.
Escapement: Set of parts (escape wheel, lever, roller) which converts the rotary motion of the train into to-and-fro motion (the balance).
Finishing: The external finishing of watches refers to the purely decorative treatment of watch surfaces. Depending on the material and colour of the surface these can include a polished, brushed, matte, gold plated or stone-set finish.
Fly-Back Hand (Retrograde Date Hand): Usually, a hand indicating a date or time against a scale which can stop independently and then 'fly-back' to catch up with 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 (Côtes de Genève): A form of decoration in higher grade watch movements in which fine lines on the movement plates create a pattern on the face of the watch. Can be applied by hand or machine. These patterns look similar to the results of a Spiro graph or Guilloché engraving.
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.
Horological: Horology is the art of making a Timepiece.
Jewel: In watch making, a synthetic ruby used for making low friction bearing in which the delicate pivots of the movement wheels run in. In some deluxe watches, sometimes sapphires or garnets are used. Expensive watch movements are jewelled from the barrel to the balance, and all automatic work, date and complication movements are expected to be jewelled.
Luminous: Key elements within the dial, on the hands or index markers are coated with a luminous material such as Superluminova to enable a user to read the time in low light or night-time conditions ensuring that the watch dial is still legible without the need for a battery powered light source.
Manufacture: A French term for a watch factory which itself produces the components needed for the manufacture of watches.
Mechanical Automatic Wind: A watch which has mechanical moving parts and winds its mainspring automatically using an internal rotor system.
Mechanical Manual Wind: A watch which has mechanical moving parts and requires its mainspring to be manually wound.
Moon-Phase Calendar: On some watches, the display of the evolution of the lunar cycle: rising, full or waning moon.
Movement: This is the internal mechanism of a watch. Assembly of parts and main components such as the mainspring, balance assembly, escapement, train of wheels, setting and winding.
Perpetual Calendar: A complication or function of a watch which displays correctly without adjustment, the day, date and month, and can also account for leap year cycles.
Power Reserve Indicator: A 'Power Reserve Indicator' shows the power resource of a mechanical movement watch.
PVD (Physical Vapour Deposition): A plating process that uses Physical Vapour Deposition as a mechanism to bond metallic and non-metallic materials such as carbon to a steel base in order to create an extermely hardwearing surface layer.
Quartz: This is awatch with a battery-powered mechanism. The quartz drives the movement by a piezoelectric effect on a tiny quartz crystal to make it vibrate, which in turn drives the mechanism and allows the watch to keep extremely consistent time.
Retrograde: This is a pointer hand on a watch dial which returns to zero at the end of a prescribed period i.e. days/months. For example a watch may have a retrograde date, meaning that the hand moves up a scale a day at a time, pointing to the current date, when it reaches 31 it will spring back to 1.
Rotor: In automatic winding mechanisms, an unbalanced, semi-circular metal turns freely in both directions winding the mainspring.
Sapphire Crystal: A Sapphire Crystal is a synthetic watch crystal that is extremely hard and very scratch resistant.
Skeleton Movement: Movement on a watch where the plates have been removed or trimmed so that you can see the gears and other parts.
Skeleton Watch: Crystal on the front and back.
Waterproof: No watch can be 100% waterproof.
Water Resistant: Describes a watch case designed to prevent water from entering.
Tachymeter (Tachometer): A watch or stop watch used for the measurement of speed. It measures speed in kilometres per hour based on 1000m distance.
Tourbillon: This type of watch is a complex piece of micro-engineering which results in the escapement of a watch rotating on its own axis; the aim is to cancel out the variations in running regularity which can be caused by the watch being in different positions; (a watch may gain in one position yet lose in another).