123 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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Watch Term Glossary

24-Hour Time

An alternative time designation to the more commonly used 12-hour time. With 24-hour time, the 24 hours and minutes of the day are numbered 00:01 to 24:00 rather than 00:01 a.m. to 12:00 midday for the first twelve hours, then 12:01 p.m. to 12:00 midnight for the second twelve hours. So 04:15 a.m. in 12-hour time is still 04:15 in 24 hour time; however 04:15 p.m. in 12-hour time is represented as 16:15 in 24-hour time. To convert 12-hour time to 24-hour time, simply add 12 to any p.m. time. To convert 24-hour time to 12-hour time, subtract 12 from any time from 13:00 to 24:00.


A sub-dial used in a chronograph function to record elapsed time. Often a chronograph watch will have two separate sub-dials, one sub-dial to record elapsed time for minutes and one sub-dial to record elapsed time for hours. Elapsed-seconds is usually recorded on the centre seconds hand. (also sometimes known as a register, counter or a totaliser)


Refers to the minimum and maximum expected rate variation of a watch over a 24 hour period. For example a watch with a published accuracy range of -10 to +25 can be expected to lose no more than 10 seconds, nor gain no more than 25 seconds, over a 24 hour period. The narrower this accuracy range, the more accurate the watch. A watch that loses or gains a very 'consistent' amount each day is considered accurate.

Acrylic Crystal

The crystal is the transparent protective cover that sits over the dial or face of a watch. An acrylic crystal is a crystal type that is made of a plastic type substance. Acrylic (plastic) is generally less expensive and less durable than alternative substances such as a 'sapphire' or a 'mineral' crystal. Acrylic crystals are also sometimes called hesalite or plexiglass. (see also Crystal)


(see Pusher, Push-Piece or Push-Button)


An Adjustment, also called a regulation, of a watch refers to the regulation process performed by a watchmaker on a mechanical watch to optimise and 'fine tune' its accuracy. This adjustment process accounts for variations in rate caused by a watch's position and sometimes other factors such as temperature and isochronism. There are various adjustments for position that a watchmaker may use to fine tune mechanical watches, these include crown up, crown down, crown left, crown right, dial up and dial down.

Aficionado (of watches)

A person that is an enthusiastic admirer, follower, fan or has a keen interest in watches and horology.


A function on a watch that will make a sound or vibration at a pre-set time.


A watch function that displays the current altitude (or height above sea level) by responding to changes in barometric pressure. An altimeter is a function commonly found in pilot watches but is also an important function for mountain climbers and rock climbers.

AM/PM Indicator

(see Day/Night or AM/PM Indicator)


Amplitude is the measure of the amount of rotation or swing of the balance wheel in a mechanical watch, expressed in degrees. The balance consists of a balance wheel that continually oscillates (rotates) backwards and forwards on its axis, each time releasing a small, incremental forward movement of the watch's escapement and gear train. Amplitude is thus the angle of rotation in degrees, of the balance wheel in each direction (clockwise then counter clockwise) away from its central position. In a well-serviced watch, the amplitude should be between approximately 275 and 315 degrees (in either a dial up or dial down position).

Analog or Analogue Watch

A watch that displays the time by means of an hour, minute and (sometimes) a second hand on the dial of the watch (as opposed to a digital watch that shows the time using a digital display).

Analog/Digital (Duo) Display (or Anadigi)

A watch that exhibits features of both analogue and digital type watch displays.

Anchor Escapement

(see Lever Escapement)


The bevelling or angled edge on a component of a watch's movement such as plate, bridge or cock. Anglage is typically undertaken for aesthetic, decorative purposes rather than for any practical purpose. In most cases the angle on the edges are formed at 45 degrees.

Annual Calendar

A calendar mechanism on a watch that adjusts automatically to account for short and long months (i.e. 30 or 31 day months). The calendar needs re-setting once every year at the end of February in non-leap years only. While not always the case, a watch with an annual calendar displays the date, the day of the week, and the month.

Anti-magnetic Watch

Magnetic fields found in typical everyday environments, such as near electronic devices and refrigerator doors, can affect the accuracy or precision of mechanical watch movements. An anti-magnetic watch is a watch that contains components or casing material specifically designed to negate or reduce the effects of these external magnetic fields. For example this includes a watch that contains materials that either cannot be magnetised or are resistant to becoming magnetised.

Anti-reflective Coating

A thin, transparent coating applied to the surface of a watch's crystal that is designed to reduce light reflection, thus increasing its daytime legibility. The anti-reflective coating can be applied to either or both sides of the crystal, with better results being obtained if both sides are treated. However, to avoid scratches on the upper layer coating, the treatment of the inner surface is often preferred.

Anti-shock mechanism

(see Shock-Resistant, Shock-Absorption or Anti-Shock)


A small opening or window on the face or dial of the watch that is used to display a certain function, such as the aperture used for displaying the day and date.

Applied Indices or Numerals (Appliqué Indices)

Raised metal indexes, numbers or batons attached to the dial via some form of adhesion.

Arabic Numerals

Dial index numbers written in the form 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12. (as opposed to the use of roman numerals or baton index markers)


An axle, pinion or pivot point of a wheel or gear component of a watch's movement, upon which the gear rotates.

Ardillon Buckle (Tang Buckle)

A traditional belt type watch band buckle in which one end of the strap is slipped through a buckle, using a pin on the buckle threaded through a hole in the strap to size and secure the band to the wearer's wrist.


The process of putting together its individual components to form the complete watch.


A scale on the dial or bezel of a chronograph watch used for measuring a persons respiration rate. A asthmometers scale is always marked with a reference number. If for example it is marked with "graduè pour 5 respirations", then the wearer would start the chronograph and count five respiration cycles. At the last (5th) beat, the chronograph would be stopped and the elapsed time seconds hand will show on the asthmometer scale what the respiration rate is. (see also Pulsometers for measuring pulse rate)

Atmosphere (ATM)

A unit of pressure used in watchmaking to indicate the degree of water resistance of the watch. Also often referred to as BAR. Where 1 ATM or 1 BAR is equivalent to 10 metres water pressure.

Authorised Dealer

A watch dealer that resells a brands watches under a direct, authorised agreement with the original manufacturer.

Automatic (Self-winding) Movement

A mechanically powered watch that is wound by the motion of the wearer's arm rather than having to be manually wound using the crown. The natural motion of the wearer causes a rotor, a semi-circler shaped piece of metal, to swivel around its pivot which winds the watch's mainspring. Many automatic watches however can also be manually wound via the crown if required. Automatic watches are also called self-winding watches.

Automatic Watch

A mechanical watch that uses an automatic movement. Automatic watches are also sometimes called self-winding or perpetual watches. (see also Automatic (Self-winding) Movement)

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