Watch Glossary

Having specialized in watches for generations, Twain Time understands that proper education is a foundation for understanding the “complicated” world of timepieces. Even the simplest of watches contains 100s of working parts. These tiny parts are all designed to fit together to make your watch tick. Glance through this glossary to gain new information, and come back if you want to know more.

12 or 24 Hour Register

The 12 or 24 Hour Register, also known as a recorder, is a sub-dial on the face of a chronograph. It can record periods of time up to 12 or 24 hours.

30 Minute Register

Just like the hour register, the 30-minute register is a sub-dial on a chronograph that records periods of time up to 30 minutes.




The alarm is a device that rings at a pre-set time.


The Altimeter determines altitude by responding to changes in the barometric pressure.

Analog Display

The Analog Display shows the time by using hands and a dial.

Automatic Winding

It is the winding that occurs through the motion on the wearer’s wrist rather than through winding the watch manually. If you haven’t worn an automatic watch for a couple of days, it’ll need to be wound again to get started again.


It’s a small opening in the dial that displays certain information such as date, day, month, or moon phase.


It’s a device that’s not affected by magnetic fields.



It is the ring on your finger or a group that plays music. When referring to watches, it’s referred to as a bracelet or strap, not a band.


Balance is the heart of the mechanical watch movement. The mainspring provides the energy, and the balance swings with the help of the hairspring to divide time into equal parts.

Balance Spring

It’s a tiny spring in mechanical watches that returns the balance wheel to its neutral position.

Balance Wheel

The Balance wheel oscillates and divides time into equal portions in mechanical watches.


One of the most famous watch shows in the world, held every year in April in Basel, Switzerland.


The bezel is the ring around the crystal on the top portion of your watch. The bezel holds the glass or crystal in place and is usually made of gold, platinum, or stainless steel.

Bi-Directional Rotating Bezel

This bezel can be moved either clockwise or counterclockwise. It is used to make mathematical calculations or keeping track of elapsed time.



A feature that shows the day of the month and sometimes even the week. Some watches with the calendar feature show the date on sub-dials. A few watches also use a scale on the outside edge of the watch dial.


Also known as a caliber, the caliber is the size or style of a watch movement.


The case is a container that protects the watch’s movement. Cases come in many shapes, round, square, rectangular, oval, and tonneau. They also give watches an attractive appearance.


It is the underside of a watch that lies against your skin. Some casebacks are made of crystal, allowing you to view the watch’s movement.


The chronograph is a watch with a stopwatch function, which measures and displays elapsed time in addition to sowing conventional time.


It is an instrument for measuring time precisely. Swiss watches must meet very high standards set by the C.O.S.C. (Contrôle Officiel Suisse des Chronomètres) to be called a chronometer. These standards include rigorous testing for 15 days and nights at five different positions and temperature changes.


A multi-part mechanism provides an additional horological function, ultimately providing more information than just the time. Complicated functions include minute repeater, perpetual calendar, Tourbillon, split-second chronograph, and others.

Cotes De Genève

It is a regular wave pattern obtained by engine-turning & polishing.


Time remaining in a predefined period.


Crown is a button, often fluted, used outside the watch case to wind the mainspring in mechanical watches. It is used to set the time when pulled out and for setting a watch calendar. A screw-down crown is also used to make the watch more water-resistant and to help keep out dust.


It is a transparent cover that protects the watch dial. Crystals are made of glass, plastic, or other synthetic sapphires. These are important as non-reflective coatings on some crystals prevent glare.


Cyclops are small lenses on the crystal to magnify the date.



These watches indicate the day of the week as well as the date.

Day/Night indicator

The Day/Night indicator is a colored or shaded band on a world time watch, which shows the time zones both in daylight and darkness.

Deployant Buckle

The Deployant Buckle fastens to the watch strap and opens and fastens with the help of hinged extenders. With this safety feature, the watch doesn’t drop when you put it on your wrist.


Destro translates to “right” in Italian. It means that the watch was intended to be worn on the right hand. It’s most commonly associated with Panerai timepieces.


Dials indicate the face of the watch. The dial holds several markings to show the seconds, minutes, hours, or any other function depending on the complications of the watch. Dials vary in shape, decoration, material, etc. The indicators are given through numerals, divisions, or symbols of various types.

Digital Watch

These watches show the time through a numerical display instead of the dial & hands like those present on an analog watch.



It’s a device in a mechanical watch that controls the motion of the hands by controlling wheel rotation.


It is the leading manufacturer in Switzerland for movements used in many Swiss brands.



The face is the visible side of the watch where the dial is positioned and printed with Arabic or Roman numerals.

Flyback (Retour en vol)

The Flyback function is beneficial to pilots because it allows the chronograph hand to be reset to zero and then immediately start again by pressing once on the push-piece.


Frequency is the number of vibrations per second in Hertz (Hz).


GMT (Greenwich Mean Time)

GMT watches possess an additional hour hand that shows two different time zones.


This precious yellow metal is stainless and very malleable. It is used in alloys to make jewelry and watches, of course. Karats (k) indicates the portion of gold in the alloy. Now you know what an 18k Gold watch means.


A style of intricate engraving that’s popular on watch dials.



This pointing device is anchored at the center of the watch. It circles the dial indicating seconds, minutes, hours, and any other special features of the watch.

High-tech Ceramic

High-tech ceramic is used as a protective shield for spacecraft reentering the earth’s atmosphere. It’s polished with diamond dust to create a highly polished finish and has a smooth surface, generally found in black but can be produced in a wide variety of colors.


Horology is the science of time measurement. It also includes the art of designing and constructing timepieces.



Synthetic rubies or sapphires that act as bearings for gears of mechanical watches. A quality automatic mechanical or hand-wound watch contains at least 17 jewels.


Karat (Carat)

A unit of gold fineness, where 24k is pure gold, and 18k gold is 75% pure.



Lugs are the extensions present on either side of the bezel. They’re positioned where the strap or bracelet is attached.


Self-illuminating paint used on hands & markers.



This term denotes a hand-wound mechanical watch.

Mechanical Movement

The Mechanical Movement is based on a mainspring that’s wound by hand. When wound, it unwinds the spring in an even motion, very slowly. Automatic mechanical watches require no winding because of the rotor, which winds the mainspring every time you move your wrist.

Military time (24-hour time)

Time is measured in 24-hour segments. To convert 12-hour time into 24-hour time, add 12 to any PM time. To convert 24-hour time back into 12-hour time, just subtract 12 from any time from 13 to 24.

Mineral Crystal

These are watch glasses that have been tempered to increase their scratch resistance.

Minute Repeater

The minute repeater is a relatively unknown complication that has the ability to strike the time in hours, quarters, or seconds through a push-piece.


The Moonphase indicator keeps track of the moon’s phases. A regular rotation of the moon around the earth is 29 days, 12 hours, and 44 minutes. Once set, this indicator accurately displays phases of the moon.


The Mother-of-Pearl is an iridescent, milky interior shell of the freshwater mollusk. What’s interesting is that it’s sliced thin and then used on watch dials. Most Mother-of-Pearl diamonds have a milky white luster, but they also come in other colors such as pink, salmon, silvery gray, and gray-blue.


Like a car cannot run without its engine, a watch cannot run without its movement. This engine of the watch is either quartz or mechanical.



Includes both Roman (I, II, III, IV, and more) and Arabic (1,2,3,4, and more) numbers to mark the hours around the dial.



Oscillation is the travel of the balance wheel from one end to the other and then back again.



Perlage, or circular graining, is a cloud-like decoration on the plates and bridges of the watch.

Perpetual Calendar

This calendar complication adjusts the watch’s calendar for different months as well as leap years.

Plastic Crystals

Plastic crystals are soft and flexible and are meant for resisting small impacts. They also enable surface scratches to be buffed out.

Power Reserve Indicator

The Power Reserve Indicator shows the remaining power in a watch movement. It also indicates the length of time until the timepiece will need to be rewound.


Physical Vapor Deposition or PVD is a thin coating applied to a case to add color for aesthetic purposes.


Quartz Movement

It’s a movement powered by a quartz crystal. In watches with Quartz Movement, the crystal oscillates to power the timepiece.

Quick-Date Quick-Set

Also referred to as Quick-Set, it is a mechanism to set the date directly to avoid turning the hands over 24 hours.


Rattrapante (Split-Second Chronograph)

A type of chronograph with two seconds hands: the second concurrently runs with the first. But the user can stop it independently to record an intermediate time.


Watches with Retrograde feature use a linear format to show the time instead of the circular dial. The hands move in an arch and then come back to the beginning.

Regulator or Regulateur

A Regulator is meant for displaying separate minute and hour hands onto a separate axial and sub-dial. It leads to accurate time telling at a glance without the chance of having the watch hands covering each other.

Rotating Bezel

A bezel around the watch that rotates if needed. Rotating Bezels have various timekeeping functions.


The rotor is an oscillating part of automatic watches that winds the mainspring.


Sapphire Crystal

It is a synthetic corundum crystal with the second-best hardness after diamond. Transparent sapphire is heavily used in watches as scratch-resistant watch crystals.

Screw Down Crown

The Screw Down Crown helps with water resistance by sealing the crown against the case.


Synthetic gaskets seal the joints between parts of the case to keep out moisture.

Shock Resistance

It is the ability to withstand normal wear and tear, even during strenuous sports activities.

Skeleton Movement

A watch with no dial exposes the movement.

Slide Rule Bezel

It’s a rotating bezel, printed with a logarithmic scale and others, mainly used with fixed rules of mathematics.

Stainless Steel

An extremely durable metal alloy immune to rust, corrosion, and discoloration. Stainless steel is highly polished sometimes. That’s why it resembles a precious metal, and since it has strength, it’s frequently used on casebacks made of other metals.

Sterling Silver

Sterling Silver, a white and highly reflective precious metal, refers to silver that is 92.5% pure. It is often used in watches that look like sterling jewelry.


The strap is basically the watchband, made of leather, plastic, or fabric.


A subdial is a smaller dial used for numerous purposes, such as indicating the date or keeping track of elapsed minutes and hours on a chronograph.

Sun/Moon Indicator

The Sun/Moon indicator is basically a wheel on a watch partially visible through a cut-out window. It indicates the sun and the moon on a 24-hour basis.


Tachymeter Scale (also known as Tachometer)

It is a common feature in chronograph watches to measure the speed over a predefined distance. One can start the chronograph when passing the starting point and stop it when passing the finish. With the tachometer scale, the wearer can even read the speed in units per hour. The Tachometer is generally engraved on the bezel, but sometimes it’s also printed on the outer diameter of the dial.

Tang Buckle

It is a traditional Loop & Pin (belt type) buckle.

Tank Watch

This is a rectangular watch with bars along the sides of its face. It was inspired by the tracks of tanks used in World War II and designed by Louis Cartier.


A timer is a device used for registering intervals of time without any indication of the time of day.


Titanium has a slightly darker/greyer appearance than Stainless Steel. Titanium is stronger and lighter than steel. Since titanium is resistant to saltwater corrosion, it’s extensively used in watchmaking, especially for sports and divers watches.


It’s a mechanism that keeps track of time and displays elapsed time, but often on a subsidiary dial.


The Tourbillon is meant for compensating differences in rate caused by a watch adopting different positions. It is a device that eliminates errors in timekeeping by balancing the horizontal and vertical positions of the balance wheel.


Uni-Directional Rotating Bezel

Typically found on divers’ watches. The bezel only rotates in a counter-clockwise direction, and its main function is overestimating the remaining air supply to prevent divers from running out of air.

Universal Time

The solar accounted for the Greenwich meridian, counted from noon to noon.



Understand this as a swing of the balance - a watch that vibrates 18,000 times an hour beats five times a second.



A misused term - no watch is 100% waterproof.

Water Resistant

Timepieces that bear the inscription water-resistant on their caseback can withstand some amount of moisture or water, such as sink splashes or thunderstorms.

Every watch has different water-resistant depths and diver’s depths:

  • Water-resistant: Water-resistant watches are okay for splashes of water or rain, but you should avoid wearing them while swimming or diving.
  • Water-resistant to 50 meters or 165 feet: Good for showering or swimming in shallow water
  • Water-resistant to 100 meters or 330 feet: Good for swimming
  • Water-resistant to 150 meters or 500 feet: Good for snorkeling.
  • Water-resistant to 200 meters or 660 feet: Good for scuba diving
  • Water-resistant to 1000 meters or 3300 feet: Good for professional deep-sea diving

White Gold

White Gold is created from yellow gold by adding nickel or palladium to the alloy to achieve a white color. Most watches that have white gold are 18k.

World Timer

These watches come with a dial that indicates up to 24 time zones worldwide. They’re usually found on the outer edge of the face or the bezel and depict the time zones indicated by major cities worldwide.


Yellow Gold

This traditional and popular color gold is used in all gold or two-toned gold watches or other precious metal combinations. You can find Yellow gold watches mostly in 14k or 18k gold.