Glossary

Alarm

A function on a watch that will make a sound or vibration at a preset time.

Altimeter

An altimeter measures altitude, or height above sea level. Recording ascent and descent, an altimeter watch is an important piece of equipment for climbers, walkers, mountaineers and, of course, aviators.

AM/PM Indicator

See Day/Night Indicator.

Analog/Digital

A watch that displays the time, both by hour and minute hands, (an analog display) and by digital digits (a digital display). This is also known as duo display or an AnaDigi watch.

Anglage

The practice of adding an angled chamfer to the edges of plates and bridges for decorative and functional purposes. Functionally, it removes sharp edges, preventing damage during service and thus eliminating debris falling into the movement.

Annual Calendar

A complication that automatically corrects the date for months with 30 and 31 days, only needing adjustment between February and March.

ATM

A measure of pressure used to define water resistance in Atmospheres. As water depths increase, so does pressure, and thus the pressure-resistance of the watch needs to be stronger to stay sealed. 1 ATM is the equivalent of 10 metres.

Automatic

A movement that can be wound both with the crown and by an oscillating weight that spins with the movement of the wearer's wrist.

Balance Wheel

The part of a mechanical watch movement that oscillates, dividing time into equal segments. This is the regulating mechanism that controls the watch's timekeeping accuracy.

Barrel

A drum that holds the Mainspring in a mechanical watch. The size of the barrel directly affects the length of the Power Reserve. Some watches feature a Double-Barrel which allows for extra long power reserve. The toothed rim of the barrel drives the train.

Bezel.

A Bezel is a ring on the top side of the case around the crystal. Some (very few) are actually located beneath the crystal. The Bezel's purpose is to measure time increments. Some bezels can be turned in only one direction - uni-direction turning bezels. Other can be turned either way - bi-directional turning bezel. Yet others are fixed and cannot be turned - each has a specific use. The purpose of the rotating Bezel is to be able to begin timing an event at any given time by aligning the bezel's #12 at the beginning point. A fixed Bezel will usually feature a scale of sorts, such as the Tachymeter scale.

BPH Beats per hour

Each rotation of the balance wheel, either clockwise or anti-clockwise, is one beat. The average mechanical watch oscillates at around 28,000 beats per hour.

Buckle

A hinged pin retainer used to latch one end of a strap to the other..

Bridge

A plate secured to the movement by at least two screws.

Brushing

Finish achieved using spinning brushed wheels of varying grades - appears as many fine scored lines over the finished surface.

Case

The metal housing that contains a watch's parts. Stainless steel is most commonly used. While titanium, platinum, gold and silver are also common, they will increase the price of the watch.

Calendar

A complication that displays the date, day, month and sometimes, year.

Caliber or Calibre

Since the early 18th Century, the calibre of a movement has denoted the position and size of its different components, notably the wheel train and the barrel. Today the term is generally used to refer to the movement, its origins or its maker.

Chronograph

A watch with a stopwatch function. A Chronograph both measures and displays elapsed times in addition to showing conventional time. Generally, the chronograph mechanism is driven by the movement of the watch and operated by two buttons on the edge of the case which start, stop and reset the chronograph. Usually the chronograph seconds hand is the large centre seconds with sub-dials for elapsed minutes and hours - although the exact display may vary.

Chronometer

Certified A movement that, when tested by an independent official body, falls within the accuracy parameters set by that body.

Co-Axial Escapement

A type of escapement patented by the late George Daniels in 1980 that considerably reduces friction and the need for lubrication.

Complication

A function in a movement. Complications vary from simple - time and date for example - to complex, like a perpetual calendar.

C.O.S.C.

The Contrôle Officiel Suisse des Chronomètres, the Official Swiss Chronometer Testing Institute that independently verifies the accuracy of tested movements.

Crown

The knob used to control the movement from the outside of the case for time and date setting and movement winding.

Crystal

The clear glass that allows the user to see the dial. Older watches will have a crystal made from acrylic, newer ones from mineral glass or synthetic sapphire.

Date

A complication that displays the days of the month as a number.

Day/Date

A complication that displays the days of the week as a word.

Deployment/Deployant Buckle

A buckle that attaches to either side of the strap. The buckle is expandable so that the watch can be slipped on the wrist and snaps shut on the wrist. Once set to the correct size it need not be resized, thus reducing stress to the strap and elongating its life. This buckle also offers additional security while putting on and taking off the watch.

Digital Display

A watch that shows the time in numbers, or digits, rather than hands and a dial. Liquid crystal display (LCD)is commonly used.

Dial

This is the face of the watch, showing the time.

Double Chronograph

A chronograph that uses two second hands simultaneously to measure split times.

Dual Time

A watch that shows local time and the time in at least one other time zone. This is generally displayed by an additional hour hand which tracks time in a 24 hour mode. Some watches have a separate sub-dial showing the full clock at the additional Time Zone.

Escapement

The device at the heart of virtually all time-keeping mechanisms. It provides the impulses to maintain the oscillations of the balance wheel or pendulum which governs the rate at which the escapement lets the wheels and hands of the watch revolve.

EOL

This is the End-Of-Life battery indication in Quartz-powered watches. Generally the seconds begin to tick once in 4 seconds indicating that the power is low and it is time to change the battery.

Equation Of Time (EOT)

An Equation Of Time (aka EOT) complication indicates the difference between "true" solar time (that of nature) and "mean" solar time (that of man). As the earth orbits around the sun in an elliptical (oval) shape and the axis is tilted - there are only 4 days a year when the day is exactly 24 hours long - April 15th, June 14th, September 1st and December 24th. All other days of the year, the days are shorter or longer - depending on the position of the earth. This watch will show the difference between the "mean" time and the "true" time. Since the number of the days are fixed year after year (at the same location) a watch can be manufactured to replicate the correction via a shaped cam which elongates and shortens the days accordingly.

Fly-back Chronograph

Retour-en-vol in French, a chronograph which restarts the instant it is brought back to zero without the need to stop, reset & restart the chronograph - it is particularly useful to pilots. Pressing the lower push-piece only, they can immediately reset the chronograph to time each successive leg of a search pattern. Without this facility they would have to use two push pieces to stop, return to zero and restart the chronograph while starting a new leg.

GMT Time Zone

Guilloché

Guilloche is an engraving technique in which a very precise intricate repetitive motif is mechanically engraved in an underlying material with very fine details. Specifically, it is a motor turning technique, called guilloche in French, by the French engineer "Guillot", who invented a machine capable of scratching fine patterns and designs on metal surfaces..

HEV (Helium Escape Valve)

Developed by Rolex alongside the commercial diving company COMEX, the HEV was an automatic valve that allowed gas to escape from a watch during decompression to prevent the crystal from popping off. I Indices Markers on the dial indicating incremental units.

Index

A simple stick / line time indicator on an analog dial, used instead of numbers.

Impermeability

A water resistant watch can resist water to some extent. Check the watch manual to find out the exact level of water resistance of the watch. The "Water Resistant" function is common in most watches. It is important to remember that the degree of water resistance is guaranteed when the watch is new and tested in ideal conditions. As the watch ages, the seals and gaskets begin to erode the drop in ratings. Therefore it is necessary to have water resistance tested every year.

Lap timer

A function in a chronograph watch that allows to know the time lap of a race. At the end of a lap, the chronograph is stopped and then returns to zero to start timing the next lap.

Lugs

The horned prongs extending from the top and bottom of a watch case onto which the strap is fixed.

Luminous

Luminous Hands and/or Hour Markers - is a standard feature on many watches. The hour markers and/or hands have a coating of "glow in the dark" which will illuminate in the dark so you can tell the time where there is insufficient light. Results vary by the amount and quality of luminous material used.

Manual Wind Movement

A Manual watch operates by manually winding the crown which winds the mainspring in the barrel, thus powering the watch. Once wound it will stay working for the specified amount of time as indicated in your manual (generally 35-45 hours).

Minute Repeater

A watch that strikes the hours, quarters and minutes on gongs. The repeater is activated by a slide or button on the case edge. This is a highly complex achievement and increases the cost of the watch tremendously.

Moonphase

A window in a watch which indicates the phases of the moon through 29 1/2 days. Some Moonphase watches incorporate a correction for the extra 44 minutes per month.

Movement

The motor of a watch that makes it keep time and perform functions.

Perpetual Calendar

A complication that displays the date, day, month and year and does not need adjusting until 2100 when the leap year will be ignored.

Platinum

Platinum is one of the rarest and most durable of precious metals. It doesn't tarnish and has a radiant, beautiful white luster.

Polished

A smooth finish that has mirror-like properties.

Power Reserve

A measure of remaining energy in a movement. Also a complication that displays the remaining energy in the movement.

PVD Physical vapour deposition

A thin chemical surface treatment that is used to apply solid colour to a material, usually metal. Not as hard or as scratch-resistant as DLC.

Quartz

The second-most abundant material in the Earth's crust, used, with an electrical impulse, to produce even oscillations from which to measure time.

Rattrapante

A chronograph that uses two second hands simultaneously to measure split times. Rotor An oscillating weight that spins with the movement of the wearer's wrist to wind the mainspring.

Sapphire Crystal

Sapphire crystal is a very hard transparent material commonly used for "scratch-proof" watch glasses. Made by crystallizing aluminum oxide at very high temperatures, it is chemically the same as natural sapphire and ruby, but without the small amounts of other elements such as iron, titanium or chromium that give the gemstones their colors. Sapphire (whether natural or synthetic) is one of the hardest substances, measuring 9 on the Mohs scale, a system for rating the relative scratch hardness of materials. (Diamond measures 10, the highest rating, and the hardest steels are 8).

Sweeping Seconds

A description of the smooth, continuous motion exhibited by the seconds hand on a traditional mechanical movement, as opposed to the staggered ticking of a quartz-powered seconds hand.

Skeleton Case

A watch case with a transparent front or back, allowing visibility of the watch's movement.

Swiss Made

A watch may only bear the Swiss-Made label if the assembly work of the movement and watch was started, adjusted and controlled by the manufacturer in Switzerland. Furthermore, the law requires that at least 50% of the components of the movement be manufactured in Switzerland. The case and bracelet must not be manufacturered in Switzerland, however the parts must be delivered to Switzerland unassemebled and be assembled in Switzerland.

Tachymeter

Common feature in chronograph watches. Measures the speed over a predefined

Time Zone

A region with a set standard of time, independent of other regions. Usually set based on the relative position of the region on the Earth's surface.

Tourbillon

The Tourbillon compensates for differences in rate caused by a watch adopting different positions. The principle is to mount the balance and escapement in a rotating cage. The balance and escapement rotate around their common axis going through all positions to average out the errors, Tourbillon cages or platforms usually rotate once per minute but 4 minute and six minute tourbillons are also found. The Tourbillon complication is an extremely difficult accomplishment to achieve and generally demands a high premium.

VPH

This refers to the movement of an oscillating element that is limited by two extreme positions. The balance of a mechanical watch usually vibrates at a rate of five or six a second, more commonly recognized by (but not limited to) 36,000 28,800 or 18,000 vph

Water Resistance

A watch that is water resistant can withstand water to a certain extent. Check the watch manual to find out the exact level of water resistance your watch is. The "Water Resistant" feature is common on most watches. It is important to remember that the water resistant rating is granted when the watch is new and tested in ideal conditions. As the watch ages the seals and gaskets begin to erode these ratings decline. Therefore it is necessary to have the water resistance tested every year.

World Time

A dial that tells the time of up to 24 time zones around the world. The names of the cities are printed on the dial. The hour in a particular zone can be read by looking at the scale next to the city that the hour hand is pointing to. The minutes are read in the normal way. The dial is usually found on the outer edge of the watch face. Watches with this function are called World Timers.

Recover password

Create my account

Glossary

Subscribe to our newsletter