Watch terminology glossary

Watch people have a vocabulary of their own. Spec sheets talk about "vph" and "jewels"; collectors talk about "grails", "lume" and "hacking". This glossary explains 79 of the most common terms in plain English, grouped alphabetically. Where we have a deeper guide, the entry links to it.

If you're completely new, start with the parts of a watch and how a mechanical watch works, then come back here as a reference.

A–B

Amplitude

How far the balance wheel swings in each oscillation, measured in degrees. Healthy watches typically swing well over 200°. Low amplitude can mean the watch needs winding or servicing.

Applied indices

Hour markers made as separate metal pieces and fixed to the dial with tiny feet, rather than printed. They catch light and add depth.

Automatic

A mechanical movement that winds itself using a rotor that spins as you move. Also called self-winding. See automatic vs manual.

Balance wheel

The weighted wheel that swings back and forth at a steady rate; the timekeeping heart of a mechanical watch.

Balance spring (hairspring)

The fine coiled spring attached to the balance wheel that makes it oscillate at a regular frequency.

Barrel

The drum that houses the mainspring. Its teeth drive the gear train as the spring unwinds.

Beat rate

How many times per hour the balance ticks, expressed in vph or bph. 28,800 vph equals 8 beats per second. See beat rate explained.

Bezel

The ring around the crystal. It can be decorative (polished, fluted, gem-set) or functional (a rotating dive or GMT scale).

Blued steel

Steel heated until a thin oxide layer turns it deep blue, at around 290°C. A classic finish for hands and screws.

bph

Beats per hour; another way of writing vph.

Breguet hands

Hands with a hollow circle ("moon") near the tip, named after Abraham-Louis Breguet. See hand styles.

Bridge

A metal plate held by screws that supports one or more wheels in the movement.

C–D

Calibre (caliber)

A specific movement design, usually identified by a number.

California dial

A dial mixing Roman numerals on the top half with Arabic numerals on the bottom. See indices and numerals.

Caseback

The back cover of the case. A display caseback has a crystal so you can see the movement.

Chronograph

A watch with a built-in stopwatch function, started and stopped with pushers.

Chronometer

A watch whose movement has been tested and certified for accuracy by an official body.

Complication

Any function beyond hours, minutes and seconds: date, moon phase, GMT and so on. See complications.

Crown

The knob on the side of the case used to wind the mainspring and set the time.

Crystal

The transparent cover over the dial: sapphire, mineral glass or acrylic.

Cushion case

A square case with softly rounded corners, popular since the 1930s. See case shapes.

Dauphine hands

Tapered, faceted hands with a ridge down the centre so one side always catches the light.

Day-date

A complication showing both the weekday and the date.

Detent

One click of the crown's ratchet as you wind.

Dial

The face of the watch that carries the markers and text.

Dive bezel

A bezel that turns only one way, used to time a dive. A bump can only shorten the time shown, never extend it.

E–G

Enamel dial

A dial coated with powdered glass fired in a kiln. Grand-feu enamel is fired at over 800°C. See dial finishes.

Escapement

The mechanism (escape wheel and pallet fork) that releases the gear train one tick at a time and gives the balance a push on each swing.

Field watch

A simple, legible, rugged style descended from First World War trench watches.

Fluted bezel

A bezel with fine ridges cut around it that sparkle as the watch moves.

Fumé dial

A "smoked" dial that fades darker toward its edge.

Gasket

A rubber seal that keeps water and dust out of the case.

Gear train

The series of wheels carrying energy from the barrel to the escapement.

Gem-set

Set with stones, each held in its own seat by tiny beads of metal.

GMT

A complication with a 24-hour hand to show a second time zone. See GMT watches.

Grail

A collector's ultimate dream watch. See what is a grail watch.

Guilloché

A dial engraved with repeating patterns on a rose engine lathe.

H–L

Hacking seconds

A feature that stops the seconds hand when the crown is pulled out, so you can set the time precisely. See how to set a mechanical watch.

Hand-wound (manual)

A mechanical movement you wind by turning the crown. See how to wind a watch.

Indices

The hour markers on the dial: batons, numerals, dots and so on.

Jewels

Synthetic rubies used as low-friction bearings for pivots. A typical movement has 17 to 25.

Lug

The horns of the case that the strap attaches to.

Lug width

The gap between the lugs, which sets the strap width — often 18, 20 or 22 mm.

Lug-to-lug

The length from the tip of the top lugs to the tip of the bottom lugs; a key measure of how a watch fits.

Lume

Luminous paint on hands and markers that glows in the dark.

M–O

Mainspring

A coiled ribbon of metal that stores energy when wound and releases it slowly to run the watch.

Manufacture

A watchmaker that designs and produces its own movements.

Mercedes hand

An hour hand with a three-spoke circle near the tip, common on divers.

Microbrand

A small independent watch brand, often selling directly online.

Milanese strap

A bracelet woven from fine steel mesh.

Minute track

The scale of minute marks around the edge of the dial. A railway track looks like train tracks.

Moon phase

A complication showing the current phase of the moon. See moon phase watches.

Mother of pearl

The iridescent inner layer of a shell, cut thin for dials.

Movement

The internal mechanism that drives the hands.

Octagon case

An eight-sided case; hard to finish because every facet must meet its neighbours perfectly.

P–R

Pallet fork

The lever in the escapement that locks and releases the escape wheel.

Pilot watch

A style with a large crown, bold numerals and high legibility, from early aviation.

Plongeur

French for diver; a style with an oversized minute hand.

Power reserve

How long a fully wound watch runs before stopping. Also a complication that shows the remaining reserve. See power reserve explained.

PVD

Physical vapour deposition: a coating a few microns thick, used to make black watches. See case materials.

Quickset date

A crown position that changes the date directly without moving the hands round.

Regulation

Adjusting a movement so it gains or loses as little time as possible.

Rose engine

A hand-cranked lathe used to engrave guilloché patterns.

Rotor

The half-moon weight in an automatic that spins with your motion and winds the mainspring.

S–T

Sapphire crystal

Synthetic sapphire; highly scratch-resistant.

Screw-down crown

A crown that screws onto the case tube for better water resistance.

Skeleton

A dial or movement cut away to show the mechanism; also a hand style with an open centre.

Small seconds

A seconds hand on a subdial rather than in the centre, usually at 6 or 9 o'clock.

Sunburst

A dial finish brushed outward from the centre so light radiates across it.

Sweep

The movement of a centre seconds hand. A higher beat rate gives a smoother sweep.

Syringe hands

Hands shaped like a syringe, common on vintage pocket and pilot watches.

Tank case

A rectangular case style dating back to 1917.

Tonneau

A barrel-shaped case that curves out at the sides.

Tourbillon

A rotating cage holding the escapement, designed to average out positional errors.

U–Z

Unidirectional bezel

A bezel that rotates only one way; standard on dive watches.

vph

Vibrations per hour. 18,000 vph = 5 beats per second; 21,600 = 6; 28,800 = 8.

Water resistance

A rating of how much water pressure a watch can handle, usually in metres or bar. It isn't a guarantee of diving depth.

Winding stem

The rod connecting the crown to the movement.

Winder

A motorised box that turns an automatic watch to keep it running when not worn.

Learn the words by making a watch

The fastest way to learn watch vocabulary is to use it. Mecha Watch lets you choose a case, bezel, dial finish, indices, hands, movement and complications on your iPhone, with a short "Did you know?" note explaining each part as you pick it. Then your watch ticks at its movement's real vph, and you wind it detent by detent. Say the name quickly — Mecha Watch — and it's an invitation to make a watch.

Frequently asked questions

What does vph mean on a watch?

Vibrations per hour — how many times the balance ticks each hour. 28,800 vph means 8 beats per second.

What are jewels in a watch?

Tiny synthetic rubies used as bearings for moving parts to reduce friction and wear. A typical mechanical movement has between 17 and 25.

What is a complication in watches?

Any feature beyond telling hours, minutes and seconds — for example a date, moon phase, GMT hand or chronograph.