The illustrated
watch glossary

Also look for: daily rate · seconds per day · s/d

How closely a watch’s indicated time agrees with a reference, often specified as seconds gained or lost over a day or month.

Also look for: plastic crystal · Plexiglas · Hesalite

A transparent plastic watch cover, often chosen for its light weight, rounded profiles, and vintage appearance.

The angle through which a mechanical watch’s balance swings from its resting position to one extreme, usually expressed in degrees.

Also look for: analogue · analog watch

A display that communicates time through pointers read against a scale, usually hour and minute hands.

Also look for: beveling · bevelling · chamfering

The finishing of an edge into a bevel, often polished on movement bridges and other components.

A calendar that accounts for 30- and 31-day months but normally needs correction at the end of February.

Also look for: AR coating · anti reflective · antireflective

A thin optical coating that reduces reflections on a crystal, helping the dial remain visible.

Also look for: applied markers

Separate hour markers attached to the dial rather than simply printed onto its surface.

Also look for: self-winding · self winding · automatic movement

A mechanical watch with a winding system that uses movement of the watch to replenish energy in its mainspring.

Also look for: balance

The wheel that swings back and forth with the hairspring to form the oscillator of a conventional mechanical watch.

Also look for: ATM · atmospheres

A pressure unit used for water-resistance ratings. One bar is approximately one atmosphere or ten meters of water-pressure equivalent.

The drum containing the mainspring. In a typical movement, its toothed rim drives the gear train as the spring unwinds.

Also look for: baton · stick hands

Straight, narrow hands with a simple bar-like outline; exact proportions vary between designs.

The ring surrounding the crystal. It may be fixed, or rotate to operate a timing or other scale.

A bezel that can rotate in either direction. Its scale determines the purpose, such as tracking a time zone or elapsed time.

A watch band usually formed from metal links, though ceramic and other materials are also used.

Also look for: pomme hands · Breguet-style hands

Slender hands distinguished by an open, off-center circular feature near the tip, associated with Abraham-Louis Breguet.

A copper-based alloy used in some watch cases and bracelets, often chosen for the patina that develops on its surface.

Also look for: satin finish · brushing

A surface finish with fine directional lines that scatter light and give metal a softer sheen.

Also look for: calibre

The designation of a movement design or model, such as NH35A. Different watch models can share a caliber.

Also look for: office GMT

A common informal term for a GMT watch whose additional 24-hour hand can be adjusted independently.

The housing that protects the movement and supports the dial, crystal, crown, and caseback.

Also look for: case size · diameter

The width across a round watch case, usually measured without the crown. Non-round cases may be specified by width and length.

Also look for: case height · thickness

The height of the watch from its back to its top surface. Check whether a quoted figure includes the crystal.

Also look for: case back

The rear cover of a watch case. It may be solid or contain a transparent window.

Also look for: high-tech ceramic

In watchmaking, a family of hard engineered materials used for components such as bezels, cases, and bracelet links.

A ring or marked zone carrying a scale around the dial, commonly for minutes or seconds.

Also look for: stopwatch

A stopwatch function that measures elapsed time separately from the normal time display.

A timepiece that has passed specified precision tests and received the relevant chronometer certification.

The fastening mechanism that closes a bracelet or strap around the wrist.

A function beyond basic time display, such as a calendar, chronograph, or additional time zone.

Also look for: Contrôle Officiel Suisse des Chronomètres · certified chronometer

The Swiss organization whose name stands for Contrôle Officiel Suisse des Chronomètres, known for chronometer testing and certification.

Also look for: winding knob

The control on the side of the case used to set the time. It can also wind or adjust other functions, depending on the movement.

Also look for: watch glass

The transparent cover over the dial and hands, commonly made from sapphire, mineral glass, or acrylic.

Also look for: date aperture · date display

An opening in the dial through which the day of the month is displayed, commonly from a rotating date disc.

Also look for: dauphine

Broad, tapered hands with a pointed, roughly triangular profile, often faceted along the center.

Also look for: day date

A display showing both the day of the week and the date of the month.

Also look for: AM/PM indicator · day night

An indication distinguishing the day and night portions of a 24-hour cycle, often for one displayed time zone.

Also look for: deployment clasp · folding clasp

A folding fastener that opens to enlarge a bracelet or strap loop without separating it completely.

Also look for: watch face

The face beneath the hands, carrying the markings and displays used to read the watch.

Also look for: digital watch

A display that presents time as changing digits rather than requiring you to read hands against a scale.

Also look for: diamond-like carbon · diamond like carbon

Diamond-like carbon: a family of hard carbon-based coatings used on some watch components.

A watch display that shows the time in two locations, using additional hands, a subdial, or another display.

Also look for: endlink · male end link · female end link

The bracelet component that meets the watch case between the lugs.

The wheel in the escapement whose teeth are repeatedly locked and released, helping transfer energy to the oscillator.

The mechanism that releases the gear train in controlled steps and supplies impulses to sustain the oscillator.

Also look for: display back · see-through caseback

A caseback with a transparent window through which you can see the movement.

Also look for: flyback

A chronograph that can reset and immediately restart a running timing measurement with one operation.

Also look for: beat rate · vph · bph · Hz · vibrations per hour · beats per hour

The rate of an oscillator’s repeating cycles. In mechanical watches, 4 Hz corresponds to eight beats per second, or 28,800 beats per hour.

Also look for: seal

A sealing element around an opening such as the crystal, caseback, or crown, helping keep moisture and dust out.

Also look for: going train · wheel train

A series of meshing wheels and pinions that transmits motion through a watch movement.

Also look for: Côtes de Genève · cotes de geneve

A decorative pattern of broad, repeated stripes applied to movement surfaces such as bridges or rotors.

Also look for: GMT · Greenwich Mean Time

A watch that can show an additional time zone, commonly using an extra hand read against a 24-hour scale.

Also look for: guilloche · engine-turning · engine turned

A decorative pattern of precisely repeated intersecting lines, traditionally cut with an engine-turning machine.

Also look for: stop-seconds · hacking

A feature that stops the seconds display when the watch is placed in its time-setting position.

Also look for: balance spring

The fine spring that provides the restoring force for the balance wheel’s back-and-forth motion.

Also look for: manual winding · hand-wound · manual watch

Winding a mechanical watch’s mainspring by turning the crown or another dedicated winding control.

The pointers that move against a dial or scale to display time or another measurement.

Also look for: indexes · hour markers · index

The markers on a dial used to identify hours or other positions on a scale.

Also look for: jewel count · rubies

Hard bearing or contact components, commonly synthetic ruby, used to reduce friction and wear at selected points in a movement.

Also look for: strap width · band width · interhorn width

The distance between the lugs at the strap attachment point, commonly expressed in millimeters.

Also look for: lug to lug · L2L · lug-to-lug length

The length from the outer tip of the upper lugs to the outer tip of the lower lugs.

Also look for: horns

The projections from the case where the strap or bracelet attaches, usually using spring bars.

Also look for: luminescence · luminous · luminous paint · Super-LumiNova · LumiBrite

The informal name for light-emitting material applied to watch displays so they can be read in darkness.

Also look for: antimagnetic · anti-magnetic · gauss

A watch’s ability to keep functioning within specified limits when exposed to a magnetic field.

Also look for: main spring

The coiled metal spring that stores the energy used to power a mechanical watch.

Also look for: METAS

A watch certification based on METAS requirements covering performance such as timekeeping, magnetic resistance, power reserve, and water resistance.

A watch powered by a mainspring, with a mechanical oscillator and escapement controlling its timekeeping.

Also look for: micro adjustment · microadjustment · on-the-fly adjustment

A way to make small changes to bracelet length, usually at the clasp, without adding or removing a full link.

Also look for: microrotor

A small automatic-winding rotor generally recessed into the movement rather than spanning most of its back.

Also look for: mineral glass · Hardlex

A glass watch cover, often strengthened by a treatment process. Hardlex is Seiko’s name for its hardened mineral glass.

Also look for: moon phase

An indication of the Moon’s phase through its roughly 29.5-day cycle.

Also look for: motion work

The gearing that links the minute and hour displays, typically making the hour hand turn once for every twelve minute-hand revolutions.

The mechanism inside a watch that keeps time and operates its displays.

Also look for: open heart

A dial with a window exposing part of the movement, often the balance wheel.

Also look for: lever

In a lever escapement, the part that alternately locks the escape wheel and transfers impulses to the balance.

Also look for: circular graining · pearlage

A decorative finish made from overlapping small circular marks, often seen on movement plates.

A calendar that accounts for different month lengths and the leap-year cycle, within the limits of its mechanism.

Also look for: polishing · mirror polish

A smooth, reflective surface finish achieved by progressively reducing surface roughness.

Also look for: running time · autonomy

How long a watch can continue running on its stored energy without being wound or charged again.

Also look for: reserve indicator · power reserve display

A display showing the watch’s remaining stored energy, usually on a scale or with an extra hand.

Also look for: push button

A button that operates a watch function, such as starting, stopping, or resetting a chronograph.

Also look for: physical vapor deposition · physical vapour deposition

Physical vapor deposition: a group of processes used to apply thin coatings to a surface.

Also look for: quartz movement

An electrically powered watch that uses a vibrating quartz crystal as its timekeeping reference.

Also look for: quick release

A spring bar with an accessible lever that retracts one end, allowing compatible straps to be changed without a spring-bar tool.

Also look for: quick-set date · quick set

A way to change the date directly, without advancing the time hands through a full day for each date change.

Also look for: model number · reference · ref

A manufacturer’s identifier for a watch model or variant, which may specify its dial, case, bracelet, or other configuration.

Adjusting a movement’s rate so that it gains or loses less time under the conditions being measured.

Also look for: oscillating weight

The weighted, rotating component that drives the winding mechanism in many automatic watches.

Also look for: sapphire glass

A watch cover made from synthetic sapphire, valued for its high resistance to scratching.

Also look for: screw-in crown · screw lock crown

A crown that threads onto a tube or fitting to secure it against the case.

Also look for: overhaul · servicing

Maintenance that can include disassembly, cleaning, lubrication, worn-part replacement, adjustment, and checks of the assembled watch.

Also look for: shock absorber

A system that allows vulnerable components, often balance-staff jewel settings, to move slightly under impact and return to position.

Also look for: skeletonized · skeletonised · openworked · openworking

A watch with movement components opened out to reveal more of the mechanism through their structure.

Also look for: subsidiary seconds

A running seconds display on its own small subdial rather than on a hand mounted at the dial’s center.

Also look for: light-powered · solar quartz · Eco-Drive

A watch that converts light into electrical energy and stores it in a rechargeable cell. Most solar watches use quartz timekeeping.

Also look for: rattrapante · split seconds

A chronograph with two superimposed timing seconds hands, allowing an intermediate time to be read while timing continues.

A small spring-loaded bar whose ends locate in holes to secure a strap or bracelet to a watch.

A Seiko-developed system powered by a mainspring but regulated electronically using a quartz reference and electromagnetic braking.

Also look for: 316L · steel

A corrosion-resistant family of steel alloys widely used for watch cases, bracelets, and clasps.

Also look for: watch band

A flexible band that holds a watch on the wrist, often made from leather, rubber, or fabric.

Also look for: sub-dial · subsidiary dial · register

A smaller dial within the main display, used for a function such as running seconds, a chronograph counter, or another time zone.

Also look for: sunray · sunburst finish · sun-brushed

A dial finish with fine lines radiating from a central point, creating shifting bands of reflected light.

Also look for: sweep seconds · smooth seconds

In everyday usage, seconds-hand motion that appears smooth rather than making obvious one-second jumps. Traditional “sweep seconds” can also mean central seconds.

Also look for: sword

Hands with a blade-like body tapering toward a pointed tip, often with a wider area for luminous material.

Also look for: tachymetre · tachymetric scale

A scale that converts elapsed time over a known unit of distance into average speed per hour.

A low-density, corrosion-resistant metal used to make cases and bracelets lighter than comparable steel designs.

Also look for: traveller GMT · flyer GMT · true GMT

A common informal term for a GMT watch with an independently adjustable local hour hand, usually moving in one-hour steps.

Also look for: dive bezel · timing bezel

A bezel that rotates in one direction only, commonly counterclockwise on a dive watch’s elapsed-time scale.

Also look for: WR · waterproof

A watch’s specified resistance to water entering the case under defined test conditions.

Also look for: worldtimer

A display designed to show the time across multiple time zones, often with city names and a rotating 24-hour ring.