Compendium of Watch Terms and Definitions

12-Hour Recorder
A stopwatch or a chronograph subdial to track 12-hour intervals.

24-Hour Time
It is often referred to as Military Time. Time is measured in 24-hour intervals instead of the 12-hour interval with AM and PM. The Military and some Eastern/European countries use the 24-hour time to avoid confusion and ambiguity.

30-Minute Recorder
This is a stopwatch or a chronograph subdial that tracks 30-minute intervals.

Acrylic
A plastic that is used to make Crystals. It’s softer than Sapphire but is easy to repair. It doesn’t shatter when broken. For this reason, many watches that are made for space use Acrylic crystals.

Alarm
A watch function that will make a sound or vibrate at the set time.

Altimeter
An altimeter measures altitude or the height above sea level. It also records the ascent and descent of height which is an important piece of equipment for pilots, climbers, hikers, walkers, and mountaineers.

AM/PM Indicator
See Day/Night Indicator

Analog
A display format using dials and hands as opposed to a digital reading.

Analog-Digital Display
Watches combining both Analog and Digital formats. Most are Quartz based watches but some can be mechanical.

Annual Calendar
The Annual Calendar is a complication that shows the date, day and the month. Some will also display the Moonphase. This watch will correctly adjust in accordance to short and long months, but will not account for leap years.

Anti-Magnetic
A type of movement in a watch that is designed to be resistant to magnetic fields that could cause inaccurate timekeeping or even adversely stop it.

Aperture
A small opening or window found on dials of certain watches where indications such as hour and date are given.

Automatic Winder
A cabinet or case with motorized rotating arms to charge Automatic watches through consistent movement. The rotations will keep the watch winding itself and thus, as accurate and consistent as it can be.

Automatic Winding (Self Winding)
Also called Automatic or Self Winding, these mechanical movements charge themselves through the motions of the wearer or an Automatic Winder. The movement either has an oscillating weight or a spinning rotor to charge it. Without consistent wear, the power reserve will exhaust and the watch will stop until it’s worn again and moved around enough to be charged. Some people find this inconvenient.

Balance Spring
A very fine spring in the mechanical movement that causes recoil of the balance wheel. The length and adjustment of its length is what regulates the timekeeping. Also known as a Hairspring.

Balance Wheel
This is the oscillator within a mechanical movement that regulates the frequency or vibration that a watch will perform at.

Barrel
A drum that holds the mainspring in a mechanical movement. The size of the barrel affects the length of Power Reserve. Some watches have a double barrel for extra power.

Bezel
The ring around the face of the watch which can be made of different materials from the body, such as Ceramic, Precious Metals or even adorn high jewelry such as Sapphires or Diamonds.

Bi-Directional Rotating Bezel
A bezel that rotates both clockwise and counter-clockwise to perform timekeeping functions.

Bracelet
The band of the watch made of adjustable links. They can be removed one at a time to fit the wearer’s wrist.

Breguet Spring
The spiral hairspring on which the balance swings will occasionally bunch on opposite sides as it contracts and expands. The constant torsion and shift in movement and gravity disturbs the rate of its balance and the problem was solved by Breguet in 1795 by raising up the last coil and giving it a smaller curve.

Bridge
A bar or a plate that is set on the movement’s main body to act as a frame. It will hold all the inner workings in place. In Skeleton Watches, the bridge is oftentimes shaped or decorated to adorn a certain aesthetic.

Calendar
A Complication that shows the date. They will sometimes even show the day of the week, month and even year. Some Calendar watches need to be adjusted manually on months that are less than 31 days long. Perpetual Calendars on the other hand, are self-adjusting and accurate over the course of years or decades.

Caliber
Movement.

Cambered
A curved or domed bezel or dial.

Case
The housing of a watch that protects the movement. It is usually made of metals and precious metals but includes other materials such as Ceramic, Plastic, Rubber, Carbon Composites and other materials depending on its purpose of functionality. The case also serves an aesthetic purpose.

Case Back
The back of the case designed to protect the movement, but also usually to open up and fix the movement if a problem should arise. Some are made of Crystal to show the inner workings. Case backs can either be screwed in or simply snapped into place with rubber gaskets to protect from dust and water. Many case backs will hold the serial number or specifications of the watch.

Chronograph
A complication that acts as a stopwatch with the precision down to a tenth of even a hundredth of a second.

Chronometer
A high precision watch with the accuracy that would be apt for navigation. Swiss made chronometers set the standards as the Swiss Official Chronometer Control (COSC) rigorously tests each watch under various temperatures and pressures.

Clasp
This is the fastening mechanism on bracelets and straps. Leather, rubber, and fabric bands most often use buckles, and bracelets or expensive leather uses deployment clasps to cause less wear on the strap.

Complication
Contrary to everyday life, a ‘complication’ in the watch world can be a good thing. The complication refers to the extra inner workings required to add other features such as a Calendar and Tourbillon.

COSC
The official chronometer testing organization COSC in Switzerland is the “Controle Officiel Suisse des Chronometres”. They set the standard bar for testing and passing chronometer testing.

Cosmograph
A chronometer dubbed by Rolex which has a tachymeter mounted on the bezel instead of on the dial.

Countdown Timer
A complication that counts down from a set amount of time. This would be ideal for timing while baking a cake or for the time winding down on a parking meter. Some can include an alarm to notify the wearer when the set time has elapsed.

Crown
A button on the side of a case that screws out, pulls out, or both. This can allow the wearer to readjust the time, date or synchronize seconds.

Crystal
The transparent cover of the Dial or Caseback. Sometimes it can be the whole case.

Cyclops
The small area on the crystal that is domed to create a magnifying lens that makes the date more legible.

Day Date
A watch with complications that show both the date and the day of the week. These watches are complex and require much more work to be created so they can be adjusted without jamming.

Day/Night Indicator
An indicator on a dual time or world time watch that shows if the home time and alternate times are in day or night. This is especially useful for watches that don’t have a 24 hour display.

Deployment Clasp
A buckle that manages to keep the bracelet or strap in one piece by opening on its hinges and fastening to itself. It may have adjustable extenders to change the length of the bracelet/strap. These are popular amongst diver or aviator watches as they may need to be adjusted to go over a jacket or wetsuit.

Dial
This is the face of the watch, including hands, marks, indicators and any subdials. Dials can be plain to intricately designed regarding the aesthetic of the watch. Some dials are Skeleton Dials, which show the inner workings of the watch without a solid face.

Digital Watch
This is a watch that shows the time or other information through a digital display instead of analog. These digital watches were first Quartz watches marketed first in the 70’s using LCD and LED displays. While in the 70’s and 80’s digital watches were novel and quite popular due to them having the futuristic features of their time, in present day they are considered retro. The resurgence of the Analog prevailed as watch connoisseurs appreciate the craftsmanship of movements dating back to the 19th century.

Diver Watch
These watches are well known for their resistance to water in depths of at least 200 m (660 ft). They are also equipped with Dials that are legible under poor light conditions and Bi-Directional Bezels for timing decompressions. Professional divers now use dive computers but many still use the Diver Watch as a backup.

Dual Time
A watch that can display two different time zones simultaneously.

Duo Display
See Analog/Digital Display.

Elasped Time Bezel
A rotating Bezel for tracking the time elapsed by setting the zero mark with the current minute hand. This way it will be easy to tell how much time has elapsed since setting the zero mark.

EOL
Some quartz watches will display an End of Life when their battery is almost drained. They can be replaced by a watchmaker or watch shop with ease.

Engine Turning
A centuries old craft that involves the use of antique machines in order to engrave delicate patterns on metal watch components which include cases, dials, movements, and bezels. Also knowns as Guilloche.

Equation of Time / EOT
This complication indicates the difference between true solar time (of nature) and mean solar time (that of man). There are only 4 days in a year where the day is exactly 24 hours long as the earth travels around the sun in an elliptical pattern instead of a perfect circular one. All the other days are either shorter or longer so in order to see the discrepancy, the EOT exists. This can be useful for outdoorsman, hunters, and sailors.

Escapement
This is the part of the movement inside a watch that divides the intervals of oscillations. There are countless versions of the escapement and most are a wonder to see within Skeleton Watches.

Face
See Dial

Field Watch
These were watches originally designed for soldiers on the battlefield. They were built simple, tough, and precise in an easy to service manner.

Flyback
This is a hand on watches and chronographs usually, that jumps back to zero. The hand on a chronograph will jump back to zero and restart timing immediately. This is a great tool to measure a series of events repeatedly.

Flyback Chronograph
A type of chronograph that can be reset without the need to stop the chronograph function. It’s very useful among pilots and users who need to record multiple times in quick succession.

Frequency
The speed at which a watch ticks or beats, measured in hertz or vibrations per hour. Most high-end mechanical watches beat at a frequency of 28,800 VpH (4Hz). Watches that beat at a higher frequency 36,000 VpH (5Hz) are considered to be high-beat watches. The frequency of a watch is controlled by the oscillations of its wheel balance.

Function
A term that describes the various tasks a watch can perform such as chronograph or altimeter. They are also known as complications.

Gasket
A rubber or neoprene plastic ring used to seal air gaps between the case and back or crystal and crown in order to prevent water and dust from entering the case and possibly damaging the movement.

Gear Train
The system of gears that transfer power from mainspring to the escapement.

GMT
This can mean Greenwich Mean Time, but a watch referred to as GMT is able to track two time zones at once. This was originally developed by Rolex for pilots and they are particularly useful for business people who travel frequently across different time zones.

Guilloche
This is an engraved ornamental pattern most often used on watch dials. It is a series of intricate intertwined lines that create an elegant pattern at first sight.

Hacking Seconds
Also known as “stop seconds” which allows the seconds on the watch to stop when the crown is pulled out. It is useful for synchronizing time with other timepieces.

Hand Wound
See Manual Winding

Haute Horlogerie
Translated from French, this term means “high watchmaking” and is used to distinguish watches or watchmakers that have extreme proficiency in technical innovation, design and aesthetics.

Helium Escape Valve
Professional diver watches are designed with a valve to let helium escape during diving. Because helium can sneak its way into a watch during deep dives, the absence of a valve would pop out the crystal on a watch from the internal pressure. The valve prevents this as divers decompress.

Horology
The art or science of measuring time.

Hybrid Smartwatch
A classical analog style watch which is usually Quartz powered but also features digital smart functions like tracking activity and push notifications.

Index Hour Marker
A stick design to indicate the hours on a dial. Also known as indices.

Indices
The marking on the watch dial that represent the hours instead of numerals.

Jewels
Synthetic rubies or sapphires that are used as bearings at the heaviest points of the movement in order to reduce the friction and overall wear. Since jewels have a naturally slicker surface, it will prolong the lifespan of the watch.

Jump Hour/Minutes
Instead of a hand continuing to move to indicate the time, a jumping display uses numerals through an aperture window which instantly change the hour or minute.

Lap Timer
A function in a chronograph that allows the wearer to time segments of a lap or race. The timer returns to zero to begin timing the next segment at the end of a lap.

Lever Escapement
A lever divides into two pallets which lock and unlock the escape wheel. The action is directed by the balance engaging the other end of this lever, as the escape teeth sliding on the inclined pallets lift the lever to engage the balance.

Liquid Crystal Display / LCD
The liquid held in a thin layer between two transparent plates shows the numeric display. The numbers are made of 7 segments that form the number 8 when all are activated by an electronic impulse.

Lugs
The protruding parts of the case at the top and bottom of a watch where the strap or bracelet attaches to. The two ends of the lugs usually hold a spring bar which will hold the bracelet or strap in place.

Luminescence
This is the glow given off by watch numerals, indices and hands that have been coated with a photoluminescent material. Watches of old would use radioactive radium but now they use non-radioactive phosphorescent materials like strontium aluminate.

Magnetism
Metal components often get magnetized when exposed to magnetic fields and causes a loss in accuracy. This can be fixed easily most of the time at home or by a watchmaker. Some companies even use silicone balance wheels or soft iron cages to protect from magnetic fields.

Mainplate
The main base on which all the parts of a mechanical watch are mounted.

Mainspring
A torsion spring which becomes tightened when the watch is wound, and in turn storing energy for the watch. The force of the spring unwinding is what powers the watch. The mainspring is housed inside a barrel, which is a small drum for encasement.

Manual Winding
A watch that needs to be wound manually in order to generate power, usually from turning the crown.

Manufacture d’Horologie
A French term which is usually shortened to ‘manufacture’ which refers to a watch company that develops its own parts at their own facilities in-house, rather than using third party suppliers and manufacturers.

Marine Chronometer
A highly accurate mechanical timekeeper which is enclosed in a box to determine the longitude aboard a ship. Marine chronometers are mounted on gimbals so they are always in a horizontal position which is essential for precision.

Measurement Conversion
This allows the wearer to convert one kind of measurement to another. It usually consists of a scale on the bezel.

Micron
A thousandth of a millimeter which is usually integrated for measuring the thickness of gold plating.

Minute Repeater
A watch that strikes the hours, quarters and minutes on gongs as the repeater is activated by a button on the case’s edge. This is a tremendously complex movement and increases the watch price drastically.

Mother of Pearl
The iridescent interior of mollusc that is often used to decorate a watch dial. Its colors can range from milky white, blue, pink, and dark to black.

Movement
This is the inner working of the watch which could either be quartz or mechanical or a hybrid. Movements are defined by, and called Calibers by most manufacturers. In a mechanical movement, the components involved are a mainspring, gear train, balance wheel and an escapement. In quartz movements, the involved parts are the battery, a microchip circuit, stepper motor and quartz crystal.

Numerals
Used to present the hour markers in Roman or Arabic.

Perpetual Calendar
A complication that shows the date, day, month and leap year cycles. Some will even display the moonphase and year. See Annual Calendar.

Platinum
Platinum is one of the most durable and rarest precious metals. It does not tarnish and has a bright and radiant luster. It is a popular choice for some of the most prestigious watches and limited edition watches.

Power Reserve
The length of time that a mechanical watch after it’s been fully wound. Most entry-level watches have about 40 hours of power reserve and many high-end watches can run for days at a time.

Power Reserve Indicator
The indicator of the state of wind in the main spring. The hand on the dial points to the number of hours a movement can work before it runs out of power. Also knowns as Reserve de Marche.

Pulsimeter
A scale on the chronograph which is used to measure pulse rate.

Pusher
The button on a chronograph that either starts/stops or resets the mechanism. Most chronographs come with dual pushers, where one is for start/stopping and the other is for resetting.

Quartz
A battery powered watch. It sends an electric signal via its microchip circuit to a small quartz crystal. This causes the crystal to vibrate at a precise rate. The vibrations then translate into the stepper motors which moves the watch hands. Quartz watches are more accurate, reliable, and cheaper, but are made of simple movements which don’t appeal to the artistry and craftsmanship that can be appreciated with their mechanical counterparts.

Rattrapante Chronograph
Double chronograph or split-seconds chronograph. It adds an additional second hand and pusher so that when both are started at the same time, the pusher can be pressed again to stop one. This is useful in recording two times at once.

Regulator
Regulators display separate hour and minute hands into axial and sub dials. This allows for quick and accurate time telling at a glance without a chance of the watch hands covering each other.

Repeater
A complication that chimes to specify the time at the push of a button on the case.

Reserve de Marche
See Power Reserve Indicator

Retrograde
An indicator on the watch dial that takes up only a segment of the circular area. When the indicator has gone through an entire cycle, it will retrograde back to the initial position by going backwards. This is often used to indicate dates, hours or minutes.

Rotor
The oscillating part of an automatic watch that winds the mainspring.

Sapphire Crystal
A very hard transparent material that is commonly used for scratch proof watch crystals. It is one of the hardest substances which rate 9 on the Mohs scale, while diamonds rate 10 and the hardest steels are at 8.

Shock Absorber
A bearing with resilience enough to take shocks and balance the staff and protect its pivots from shock damage.

Silicon
This material is becoming popular in movements for their anti magnetism and anti temperature properties. It also doesn’t require lubrication. Thus, watches with silicon components are usually more accurate and resilient.

Skeleton
A skeleton watch shows off the inner workings of the watch through where the dial should be, or a partially cut out portion of the dial. This gives a new appreciation for the craftsmanship of mechanical movements.

Small Seconds
A small sub dial placed within the main dial that shows seconds separately.

Solar Powered Watch
Batteries in a quartz watch are recharged by solar panels on the watch face.

Stainless Steel
A durable and sturdy metal alloy that is almost rust resistant and rarely discolors or corrodes. It is highly suitable for watches and is usually the go-to for most standard watches and bracelets.

Stepping Motor
Part of a quartz analog movements which moves the gear train and thus, the watch’s hands.

Sterling Silver
This is a highly reflective precious metal which is 92.5% pure and is often used in dials and watches.

Subsidiary Dial
A sub dial on the watch face used for indicating things such as the date, power reserve or elapsed time.

Tachymeter / Tachometer
Measures the speed over a defined distance. The wearer can start the chronograph at the starting point and stop at the finish line and the speed per hour will be comprehensible on the tachometer scale. Mostly the scale is engraved on the bezel or printed on the outer lining of the dial.

Tang Buckle
Traditional loop and pin buckle much like a belt.

Tank Watch
Rectangular watches with bars along the sides of its face which were inspired by tank tracks during WWII and created by Louis Cartier.

Timer
Device or function registering intervals of time without any indication of time of day.

Titanium
Stronger than steel and slightly darker. It is lightweight and durable and resistant to salt water corrosion which is why many water sports and diver watches utilize titanium now.

Tourbillon
This is a type of escapement which is housed in a rotating cage and is meant to counter the negative effects of gravity on the movement. While this movement was originally intended for pocket watches, they have moved to wrist watches to exemplify the watchmaking capabilities of the manufacturer. As such, the prices are exorbitant.

Winder
See Automatic Winder

World Timer
A watch with a dial that can show times in 24 different time zones represented by the 24 major cities across the world.