Acrylic Crystal

Acrylic is a type of plastic used for making crystals before harder materials like synthetic sapphire became available. It is typically thicker and more prone to scratching than a sapphire crystal.

Alarm

An alarm is a functionality in timepieces that utilises sound and, sometimes, vibration to alert the user at a predetermined time. It is predominantly integrated into quartz watches, and to a lesser extent, mechanical timepieces.

Amplitude

The balance wheel moves in both clockwise and counterclockwise directions, creating a specific angle of rotation known as the amplitude. This angle typically falls between 275 and 315 degrees.

Ana-digi

A watch that features both analogue displays (hands) and digital displays (numerals). Often powered by quartz movements, although there are exceptions.

Analogue

A method of representing time using a continuously varying display, typically with rotating or pivoting hands.

Anglage

Anglage is the practice of adding an angled chamfer to the edges of plates and bridges for both decorative and functional purposes. This technique serves to remove sharp edges, thus preventing damage during service and eliminating debris from falling into the movement.

Annual Calendar

The annual calendar has a feature that automatically adjusts the date for months with 30 and 31 days. It only requires adjustment between February and March.

Anti Magnetic

When a watch is said to be anti-magnetic, it means its internal movement is shielded from magnetic fields. This is important because magnetism can disrupt a watch’s accuracy.

Aperture

The aperture is the cut-out on the watch dial that is used to view the date wheel.

ATM

ATM, represents a measure of pressure utilised to gauge water resistance. With increasing water depths, there is a corresponding increase in pressure, necessitating a stronger pressure-resistance in watches to maintain a sealed state. One ATM is equivalent to 100 meters in depth.

Automatic

An automatic, or self-winding, movement in a timepiece refers to a mechanism that utilises the motion of the wearer’s arm to drive a rotor, which in turn winds the mainspring via specific gears. This method of generating power eliminates the need for manual winding, although some automatic movements do offer the option of manual winding, particularly those with extended power reserves.

Balance Wheel

The balance wheel is a small wheel, approximately one centimetre in diameter, which is equipped with a hairspring. It is a component of the escapement and it plays a crucial role in regulating the power from the mainspring and transferring it back into the movement in controlled, regulated bursts. This is achieved by the wheel spinning repeatedly in both clockwise and anti-clockwise directions.

Barrel

A Barrel is a short, cylindrical container in a watch that holds the coiled mainspring. Some watches have one, while others have more, typically indicating a higher power reserve.

Base Plate

The base plate is the foundation of the movement to which the other components are attached. The dial is mounted on the underside.

Bead-Blasting

Bead-blasting is a process that creates a matt finish by shooting numerous tiny glass beads at high pressure.

Beat

Each rotation of the balance wheel, either clockwise or counterclockwise, is one beat. The average mechanical watch oscillates at around 28,000 beats per hour. (see BPH)

Bevelled Edges

Bevelled Edges, refers to incorporating an angled chamfer to the edges of plates and bridges for decorative and functional purposes. This technique serves a functional role by eliminating sharp edges, which in turn helps prevent damage during service and reduces the risk of debris falling into the movement.

Bezel

The bezel is the protective metal ring that surrounds the watch crystal. It can be taken off the case for repair or replacement. Some bezels are designed to rotate in one or both directions for timing or to track different time zones.

Bluing

Bluing is a process used to both decorate and protect steel from corrosion by imparting a blue colour. This can be achieved through traditional heating methods or more contemporary chemical treatments.

Bottom Plate

The bottom plate serves as the foundational attachment point for the movement, onto which the remaining components are affixed. The dial is positioned and secured on the underside of this base.

BPH

BPH stands for 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.

Bracelet

A watch strap, referred to as a bracelet, is comprised of a chain of interconnected solid metal pieces.

Breguet Overcoil

The outermost coil of the balance wheel hairspring is intricately twisted back over itself and secured at a midpoint along its width. This configuration safeguards against the spring’s deformation during expansion and contraction, thereby upholding a consistent and stable oscillation.

Bridge

A Bridge is a plate that is fastened to the movement using at least two screws.

Brushing

A textured finish is attained by utilising rotating brushed wheels with varying grades, resulting in the creation of numerous fine-scored lines across the finished surface.

Buckle

A buckle is a fastening device consisting of a frame and a hinged pin, which is used to securely fasten one end of a strap to another.

Cabochon

A cabochon refers to a polished precious or fine stone that has been cut into a smooth, rounded dome shape without any facets. One famous use of cabochons is by Cartier, which has used blue cabochons to adorn the crowns of its watches. Additionally, cabochons can be utilized to embellish the dials of watches.

C.O.S.C.

Contrôle Officiel Suisse des Chronomètres (COSC), is the Official Swiss Chronometer Testing Institute. This independent organisation rigorously tests and verifies the accuracy of watch movements, ensuring that they meet the highest standards for precision and reliability.

Calendar

The calendar complication is meant to provide a visual representation of the current date, day of the week, month, and occasionally the year.

Caliber/Calibre

Caliber/Calibre refers to the specific model or design of a movement within a watch or timepiece. This term is commonly used in horology to distinguish between different types of movements based on their specifications and characteristics.

Case

The housing that contains the movement, dial, and hands, usually made of metal.

Caseback

The caseback refers to the push-fit or screw-down cap located on the rear of the case. It is frequently equipped with a display glass to allow viewing of the movement within.

Case Middle

The case middle is the central part of the watch case that holds the movement. The back and bezel are attached to the case middle, and it is sometimes made from a different material to ensure strength and rigidity.

Centrelinks

Centerlinks are the middle section of a three-piece watch bracelet link.

Chapter Ring

A chapter ring is a spacer used to fill the vertical void between the edges of the dial and crystal, often with minute markers applied to it.

Chronograph

A chronograph is a watch complication that allows the user to measure a specific period of time from the starting point.

Chronometer Certified

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

Clasp

A clasp is a secure folding system made of metal, used to fasten a bracelet together.

Clous De Paris

The Clous De Paris, commonly known as “hobnail” in English, refers to a guilloche pattern present on the hollowed lines of a watch dial, creating intersecting tiny pyramidal shapes. This decorative technique can also be found on the bezel of timepieces, such as the beautiful Patek Philippe Calatrava 6119R.

Co-Axial Escapement

An escapement type patented by George Daniels in 1980, which significantly reduces friction and the need for lubrication.

Cock

A cantilevered metal plate that is fastened to the movement at one end only.

Column Wheel

The column wheel in a chronograph has a castle turret-like shape and coordinates the engagement of the chronograph using gear meshing instead of vertical friction.

Complication

A function within a watch movement. It can be as simple as displaying time and date or as complex as a perpetual calendar.

Corrector

Many timepieces equipped with indicators such as the date and moonphase also feature a discreet corrector button integrated into the case middle. This unobtrusive button is utilised with a specialised tool to make adjustments, or corrections, to the various indications as necessary.

Côtes de Genève

A type of decoration often found on movement plates is Côtes de Genève, usually consisting of tightly packed curved lines engraved along the length of repeating thick strips.

Crown

The crown, is a small knob situated on the exterior of the case. It is utilised for setting the time and date as well as for winding the movement.

Crown Guards

Crown guards are protruding shapes on the case designed to protect the crown from impacts.

Crystal

The crystal is the clear glass component that enables the user to observe the dial of a timepiece. While older watches feature a crystal crafted from acrylic, newer models utilise materials such as mineral glass or synthetic sapphire.

Cushion Case

A transitional design that combines aspects of both rectangular and round cases.

Date

A feature that shows the days of the month as numbers.

Day

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

Dead-Beat Seconds

The feature referred to as “Dead-Beat Seconds” describes the movement of the seconds hand once per second. This is a characteristic commonly found in quartz watches and is considered a rare and intricate feature in mechanical watches.

Decimal Repeater

The timepiece is equipped with a complication that strikes the hours, the number of ten-minute periods since the hour, and the minutes using a series of gongs upon command.

Decoration

The process of applying finishes to enhance the aesthetics of a watch or its components.

Deployant

The part of the watch that shows the time and other functions

Dial

The part of the watch that shows the time and other functions.

Display Back

The “Display Back” refers to a caseback with a glass window that allows for viewing of the movement inside.

Diver’s Extension

A folding extra link in a bracelet that allows a diver’s watch to fit over a diving suit without the need for tools.

DLC

Diamond-Like Coating (DLC) is a chemically-deposited protective layer designed for metal surfaces. This coating, typically black in color, is highly durable and offers superior scratch resistance compared to PVD coatings, although it is not entirely scratch-proof.

Double Axis Tourbillon

The Double Axis Tourbillon is a mechanism designed to rotate the tourbillon cage and escapement through a second axis in addition to the traditional first axis.

Double Chronograph

A chronograph that employs two second hands concurrently to measure split times.

Dual Time Zone

A dual time-zone watch has the capability to concurrently display two distinct time zones, typically indicating the wearer’s local time and the home time.

Endlinks

Endlinks are the components that connect the bracelet to the case.

Equation of Time

The “Equation of Time” is a sophisticated complication designed to gauge the disparity between apparent solar time and mean solar time.

Escape Wheel

The escape wheel is a gear with sharp teeth that interacts with the pallet fork. It’s a crucial part of the escapement and plays a key role in transferring power from the mainspring back into the movement in a controlled manner. This is achieved by its engagement with the pallet fork, which locks and releases it in regulated intervals.

Escapement

The escapement is a crucial part of a watch’s movement that regulates the release of power from the mainspring. It consists of the balance wheel, pallet fork, and escape wheel. As the balance wheel swings back and forth, it moves the pallet fork from side to side, engaging and disengaging with the escape wheel, which in turn controls the movement’s power.

Exhibition Back

A caseback with a glass window for viewing the movement is called an exhibition back.

Finish

The finish refers to the appearance of a material that has been subtly decorated, for example, through polishing, brushing, or bead-blasting.

Five-Minute Repeater

A Five-Minute Repeater is a complication that strikes the hours and the number of five-minute periods since the hour on command using a series of gongs.

Flyback

A flyback is a type of chronograph complication that allows the seconds hand to be instantly reset and restarted during timing.

Flying Tourbillon

A flying tourbillon is a mechanism supported by a cantilevered bridge (called a cock) instead of a traditional spanning bridge.

Folding Buckle

The folding buckle, also known as a deployant buckle, is an articulated closure that unfolds upon opening. This design ensures secure attachment of the watch to the wrist and is commonly featured on sports and tool watches. In the event of accidental opening, the buckle will still adequately secure the strap, preventing the watch from slipping off the wrist.

Foudroyante

Foudroyante is a chronograph complication that displays seconds in 1/8th segments.

Four Year Calendar

Four-year calendar complication displays the date, day, and month and only requires adjustment on a leap year.

Frequency

A measure of frequency is the number of repetitions per second, measured in Hertz (Hz), such as the oscillations of a balance wheel.

Fusee

A fusee is a conical spiral gear that a chain winds around.

Gasket

A gasket is a thin piece of material, typically rubber, that is compressed between two components to create a seal.

Gear Train

An arrangement of differently sized gears aligned to achieve a specific speed of rotation.

Geneva Seal/Hallmark

The official seal of the city of Geneva, Switzerland is given to watches that meet an extremely high standard of construction and finishing.

Geneva Stripes

A type of decoration often found on movement plates, usually consisting of tightly packed curved lines engraved along the length of repeating thick strips.

GMT

Greenwich Mean Time is the original standard of time and still serves as the basis for all other time calculations.

Grand Sonnerie

Grand Sonnerie is a complication that strikes the hours on command and also strikes the number of hours and quarters every quarter using a series of gongs.

Guilloche

Guilloche is the creation of intricate and precise mathematical patterns using engraving.

Hacking Seconds

Stop the seconds hand when setting the time for more accuracy.

Hairspring

The coiled spring fitted to a balance wheel that allows it to oscillate clockwise and counterclockwise repeatedly.

Hallmark

A stamped code found on precious metals that indicates its origin and verifies its authenticity.

Hands

A long, slender pointer that moves along a scale to show a measurement or unit.

Hand-wound

A mechanical movement that needs the crown to be rotated in order to wind the mainspring.

Hertz

Hertz is a unit used to measure the frequency of a periodic event. It is equivalent to one cycle per second.

Hesalite

Hesalite is the brand name for Omega acrylic crystals.

HEV

Helium Escape Valve. Developed by Rolex in collaboration with the commercial diving company COMEX, the HEV is an automatic valve that releases gas from a watch during decompression to prevent the crystal from popping off.

Horology

A fascinating field, encompasses the intricate study of time and the measurement of its passing through various methods and technologies.

Hunter Case

The term “Hunter Case” is used to describe a type of watch case that has both a front and back cover, typically connected by small hinges. These covers serve to protect the dial and caseback from dust and potential damage, and they are sometimes intricately decorated or engraved with a coat of arms or similar designs. A watch case with only one cover, usually on the back, is known as a Half-Hunter.

Incabloc

Incabloc is a brand of spring-loaded shock protection used on balance wheel-supporting jewels to absorb sudden, potentially damaging impacts.

Index

The index, also known as the regulator, is used to adjust the rate of a watch by increasing or reducing the effective length of the balance spring. It is a steel lever with a shorter end that holds the curb pins embracing the spring and a longer end that passes over a scale marked with F for fast and S for slow.

Indices

Indices are markers on the dial that indicate incremental units.

Jewels

Bearings made from synthetic rubies offer high wear resistance and low friction, providing a modern solution for efficient functionality.

Jumping Hours

The “Jumping Hours” feature refers to an hour indicator that moves instantly from one hour to the next, rather than slowly progressing from one hour to the next.

Large Date

The large date display, also known as an outsize date or panoramic date, is a type of date display found in some watches. Unlike a standard date display, which typically shows the date on a single rotating disc, the large date display features two large numerals on two separate discs. These numerals are usually displayed through oversized apertures, providing a unique and easily readable way to view the date on the watch dial.

LCD

LCD is an abbreviation for Liquid Crystal Display, an electronic visual display that uses the light-modulating properties of liquid crystals. LCDs are commonly utilised to present information such as numbers or text in digital devices.

Lugs

The “Lugs” are the horned prongs that extend from the top and bottom of a watch case, onto which the strap is fixed.

Lug Width

The lug width of a watch refers to the distance between the lugs, which in turn determines the appropriate width of the watch strap or bracelet for the case. It is essential to verify this measurement before purchasing a replacement strap or bracelet for your watch.

Lume

Lume is a material, usually a type of paint, that is used on watches to make them glow in low light conditions. In the past, it was made with radioactive materials such as radium and tritium, but nowadays it is produced with non-radioactive substances.

Luminova

Luminova is a reputable brand known for its production of non-radioactive luminous paint, offering a safe and sustainable solution for various applications.

Main Plate

The main plate is the base of the movement onto which the rest of the movement is attached. The dial is mounted on the underside.

Mainspring

A mainspring is a coiled length of metal strip that provides power to the movement once wound.

Manual

This term refers to a mechanical movement that requires rotation of the crown to wind the mainspring.

Manufacture

The term “manufacture” is often used in the Swiss watch industry to distinguish between a company that makes a watch almost completely in-house and those that buy parts from outside suppliers and then assemble, time, and add the hands and movement to the watch.

Marine Chronometer

The marine chronometer is the first portable clock accurate enough to calculate longitude.

Mechanical

This refers to a movement consisting of clockwork parts with no electrical assistance.

Micro-Rotor

A micro-rotor is a self-winding, oscillating weight smaller than a standard, full-size rotor.

Mineral Crystal

A mineral crystal is a cheaper alternative to synthetic sapphire for watch glass, but it is not as scratch-resistant.

Minute Repeater

The minute repeater is a complication that strikes the hours, quarters, and number of minutes since the quarter on command using a series of gongs.

Moonphase

The moonphase is a complication that displays the stages of waxing and waning through the lunar cycle.

Movement

A movement refers to the engine that powers and drives a watch.

O-Ring

A thin piece of material, typically rubber, that is compressed between two components to create a seal.

Oscillating Weight (Rotor)

The oscillating weight, also known as the rotor, is a crucial component found in automatic (self-winding) watch movements. It is a hefty metal disc that rotates freely in both directions to wind the mainspring. The rotor is often embellished or decorated to add visual interest to the watch movement.

Pallet Fork

A pallet fork is a lever with two prongs at one end, each mounted with a synthetic ruby tooth. It is part of the escapement and helps to regulate the release of power from the mainspring back into the movement in controlled bursts by rocking back and forth to lock and release the escape wheel.

Perlage

Perlage is a decoration that consists of repeated circular graining, usually found on metal surfaces.

Perpetual Calendar

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

Pin Buckle

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

Pinion

A pinion is a small, round gear, typically the smallest in a gear train.

Polished

“Polished” refers to a smooth finish that has mirror-like properties.

Power Reserve

Power reserve is a measure of the remaining energy in a movement and can also be a complication that displays the remaining energy in the movement.

Pushers

Pushers are buttons used to activate complications such as a chronograph. It is important not to operate pushers in wet environments or when the watch is submerged.

PVD

PVD stands for physical vapour deposition, a thin chemical surface treatment used to apply solid colour to a material, usually metal. It is not as hard or scratch-resistant as DLC.

Quarter Repeater

This is a feature in a timepiece that chimes the hours and the number of quarters since the last hour upon activation, using a series of gongs to produce the sound.

Quartz

Quartz is the second most abundant material in the Earth’s crust. When used with an electrical impulse, it produces regular oscillations that are used to measure time accurately.

Quickset Date

Quickset Date is a useful feature in a watch that allows the wearer to independently adjust the date using the crown, without needing to manually advance the time through a full twenty-four hour period.

Radium

Radium is an extensively radioactive material historically employed in the production of luminescent paint for watch dials during the early 20th century.

Rattrapante

Rattrapante refers to a type of chronograph featuring two independent second hands that concurrently measure split times.

Regatta

Regatta is a complication traditionally utilized by sailors to time the ten-minute countdown prior to the start of a race.

Regulation

Regulation denotes the fine adjustment of a movement’s beat to enhance its accuracy.

Rehaut

Rehaut is a term used to describe a spacer that fills the vertical void between the edges of the dial and the crystal.

Repeater

A repeater is a complication that, upon activation, strikes the time using one or more gongs.

Retrograde

Retrograde denotes a non-circular, linear scale with an indicating hand that instantaneously returns to the start upon reaching the end.

Rotor

A rotor is an oscillating weight that rotates with the wearer’s wrist movements, winding the mainspring of the timepiece.

Rubies

Rubies are bearings known for their high wear resistance and low friction, commonly constructed synthetically in modern times.

Sand-Blasting

This technique involves achieving a matte finish by propelling sand at high pressure onto the surface.

Screw-Down Crown

The screw-down crown creates a water-resistant seal between the crown and the case using a threaded design and o-rings.

Shock Resistance

The mechanism utilises spring-loaded shock protection on balance wheel-supporting jewels to effectively absorb sudden, potentially damaging impacts.

Sidereal Time

Astronomers use this method of timekeeping to track the orientation of the night sky.

Skeleton

This technique involves reducing a component, often the movement, to its barest minimum, creating the layered skeleton effect.

Solar Power

A watch, typically quartz, that is capable of drawing and storing charge from light.

Spring Bars

These are spring-loaded tubes used to secure a strap to a watch case by pinning it between the holes in the lugs.

Stem

The threaded bar that connects the crown to the movement inside the watch.

Strap

A band that attaches the watch case to the wrist.

Sub-Dial

A smaller dial located within the main dial, often used to display additional information or complications.

Super-Complication

A watch that incorporates numerous complicated features.

Super-Luminova

A well-known brand of non-radioactive luminous paint used for watch markings and hands.

Sweeping Seconds

This term describes the smooth, continuous motion exhibited by the seconds hand on a traditional mechanical movement, in contrast to the tick-tock motion of a quartz-powered seconds hand.

Synthetic Sapphire

An extremely hard and scratch-resistant material commonly used to make watch crystals.

Tachymeter

The Tachymeter scale is commonly engraved on the bezel of sports watches with a chronograph function, often seen in racing-inspired designs. This scale can be used to calculate speed based on travel time or measure distance based on speed. The spacing between the marks on the Tachymeter dial corresponds to 1/t, where ‘t’ represents the elapsed time.

Time Zone

A time zone refers to a specific region with a defined standard time, which is independent of other regions. This standard time is usually determined based on the geographic position of the region on the Earth’s surface.

Tonneau

The tonneau case shape represents a style that sits between a rectangular case and a round case, featuring softened edges and a distinct barrel-like silhouette.

Tourbillon

A tourbillon is a complex horological feature that includes a rotating escapement, designed to counteract the adverse effects of gravity on a watch’s accuracy. This intricate mechanism is often visible through the watch’s dial.

Tritium

Tritium is a radioactive material that was commonly used in the mid-20th century to create luminescent paint on watch dials. It emits low levels of radiation and provides long-lasting luminescence in low-light conditions.

Twenty-Four Hour

The twenty-four-hour timekeeping format is a method of tracking time that spans an entire 24-hour day in a continuous scale, offering an alternative to the standard 12-hour format.

UTC

Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time. It is based on the time at the prime meridian (0 degrees longitude) and is closely related to Greenwich Mean Time (GMT). UTC is used in aviation, weather forecasts, telecommunications, and other scientific disciplines.

Unidirectional Bezel

The unidirectional bezel on a diving watch is intentionally designed for safety. It only turns in one direction, which helps to reduce dive time. This feature ensures that if the bezel is accidentally turned, the diver can still surface with enough air and properly observe decompression stops.

Vibrations

In a watch, each swing of the balance wheel, in either direction, is considered one vibration. A typical mechanical watch oscillates at a rate of around 28,000 vibrations per hour.

VPH

VPH refers to the number of vibrations occurring in an hour. In a watch, each swing of the balance wheel, in either direction, is considered one vibration. A typical mechanical watch oscillates at a rate of around 28,000 vibrations per hour.

Water Resistance

Water resistance refers to the ability to maintain a seal when submerged at increasing depths of water. It is usually expressed as a rating of depth in meters (m) or pressure in Atmospheres (ATM).

Wheel

A wheel is an alternative name for the gears that are used to transfer power through a movement.

ZULU Time

ZULU Time, also known as Greenwich Mean Time (GMT), is a standard time reference used widely in military operations and communications. It is especially important for coordinating activities across different time zones and ensuring precise synchronisation.