Watch Glossary

A

Antimagnetic Watch
A watch built to resist magnetic fields up to a certain strength without losing accuracy. To be officially labeled “antimagnetic,” it must meet the ISO 764 standard.

Anti-Reflective Coating
A thin treatment applied to watch crystals to reduce glare. This improves clarity and makes the dial easier to read under direct light.

Automatic (Self-Winding)
A type of mechanical watch that winds itself using a rotor inside the movement. As the wearer’s wrist moves, the rotor spins and winds the mainspring. To prevent overwinding, automatic watches include a slip mechanism in the mainspring.

B

Bakelite
One of the first synthetic plastics, created in the early 1900s by chemist Leo Baekeland. It was once widely used in everyday objects such as radios, knobs, and steering wheels, and even in early watch bezels.

Balance Wheel
The “heart” of a mechanical watch, swinging back and forth at a steady rate to regulate timekeeping. It works with the hairspring and performs the same function as a pendulum in a clock—only much faster.

Bar (Pressure Measurement)
A unit of pressure often used to indicate water resistance.

• 1 bar ≈ air pressure at sea level

• 1 bar ≈ pressure at 10 meters underwater

Barrel
A drum-shaped component that houses the mainspring, storing energy to power the movement.

Bezel
The ring that surrounds the watch crystal. On dive watches, it often rotates to track elapsed time. On chronographs, it might include a tachymeter scale to measure speed.

Breguet Overcoil
A special design for the end of a hairspring, invented by Abraham-Louis Breguet. The raised outer coil helps the spring breathe evenly, improving accuracy.

C

Calendar Watch
Any watch that displays calendar information. Variations include:

• Date – shows the day of the month.

• Day-Date – shows both the day of the week and the date.

• Annual Calendar – corrects itself for months with 30 or 31 days, needing adjustment only once a year in February.

• Perpetual Calendar – automatically adjusts for leap years and doesn’t need manual correction until the year 2100.

Caliber
Another word for movement. Manufacturers often use it with a number (e.g., Caliber ETA 2824-2).

Central Seconds
A seconds hand placed in the center of the dial, on the same axis as the hour and minute hands.

Cerachrom
Rolex’s proprietary ceramic material, highly resistant to scratches and fading, used for modern bezels.

Chamfering (Anglage)
A decorative finishing technique where sharp edges of movement parts are beveled and polished at 45 degrees.

Chime
A function where a watch sounds the time using gongs or bells.

Chronograph
A watch with a stopwatch feature, operated by pushers that start, stop, and reset the timing hand.

Chronometer
A mechanical movement tested for superior precision, often certified by the COSC in Switzerland.

Clasp
The closure system on a strap or bracelet. Examples include tang buckles, deployant clasps, and butterfly clasps.

Co-Axial Escapement
An escapement design created by George Daniels and popularized by Omega, reducing friction and improving long-term accuracy.

Complication
Any additional function beyond hours, minutes, and seconds (such as a chronograph, moonphase, or GMT).

Compressor Case
A special case design patented in the 1950s, where water pressure actually helps tighten the seals. Popular with vintage dive watches.

D

Display Case Back
A transparent case back, often made of sapphire crystal, that allows you to view the movement.

Diver’s Watch
A watch designed for underwater use, typically water-resistant to at least 100 meters and featuring a rotating bezel, luminous hands, and screw-down crown.

Double Barrel
A movement that uses two mainsprings, usually for extended power reserve.

Double Chronograph (Rattrapante)
A chronograph with two seconds hands, allowing you to time multiple events simultaneously.

E

Escapement
The mechanism that regulates the release of energy from the mainspring to the balance wheel. It ensures steady, controlled ticks.

Escape Wheel
A gear within the escapement that works with the pallet fork to drive the balance wheel.

ETA
A major Swiss movement manufacturer (part of the Swatch Group), supplying calibers to countless watch brands.

Everose Gold
Rolex’s proprietary 18k rose gold alloy, engineered to maintain its color and resist fading.

F

Finishing
The art of decorating a movement’s components, both for aesthetics and prestige. Examples include Geneva stripes, perlage, and blued screws.

Flyback Chronograph
A chronograph that can be reset and restarted with a single push, useful in aviation and racing.

G

Gauss
A unit used to measure magnetic fields. Watches resistant to magnetism are often rated in gauss (e.g., Rolex Milgauss resists 1,000 gauss).

Geneva Seal
A hallmark of quality awarded to movements made in Geneva that meet strict standards of finishing and performance.

Geneva Stripes
Decorative parallel stripes applied to plates and bridges of movements, also called Côtes de Genève.

GMT (Greenwich Mean Time)
A function that tracks a second time zone using an additional hand.

Guilloché Dial
A dial engraved with intricate, repeating patterns, either by hand or machine.

H

Hairspring
A thin, coiled spring attached to the balance wheel, responsible for regulating its oscillations.

Helium Escape Valve
A valve found on professional dive watches, designed to release trapped helium gas during decompression.

I

Indices
The markers on a watch dial that represent hours or minutes, which may be numerals, batons, or applied shapes.

L

Lugs
The parts of the case that extend out to hold the strap or bracelet.

Lug Width
The internal distance between lugs, which determines strap size.

Lume
The luminous material applied to hands and indices, allowing them to glow in the dark. Modern watches typically use Super-LumiNova.

M

Mainspring
The tightly wound spring inside the barrel that stores energy for the movement.

Manual-Wind
A mechanical watch that must be wound by turning the crown.

Master Chronometer
A certification developed by METAS in Switzerland, ensuring accuracy, durability, and resistance to magnetic fields up to 15,000 gauss.

Minute Repeater
A highly complex complication that chimes the time on demand.

Moonphase
A complication that displays the current phase of the moon on the dial.

Moonwatch
A nickname for the Omega Speedmaster Professional, worn during NASA’s Apollo missions and the first moon landing.

N

NATO Strap
A durable, military-inspired strap made of nylon or fabric that passes under the case, adding security if a spring bar fails.

P

Pallet Fork
A Y-shaped lever in the escapement that transfers energy from the escape wheel to the balance wheel.

Parachrom
Rolex’s proprietary hairspring alloy, resistant to magnetism and temperature changes.

Pilot’s Watch
A watch designed for aviation, typically with a large, easy-to-read dial and oversized crown.

Power Reserve
The amount of time a watch can run after being fully wound.

Power Reserve Indicator
A display that shows how much energy remains before the watch needs rewinding.

Plexiglass
A type of acrylic crystal once commonly used in watches, lightweight and shatter-resistant, though prone to scratches.