A–Z Glossary of Horology & Mechanical Watch Terminologies You Should Know
- Huan Ni
- Nov 15
- 5 min read
When it comes to keeping time, every minute detail matters, and so does every word.
The world of horology is actually rich with terminology that reflects the precision, artistry, and legacy behind each timepiece. Whether you're a seasoned collector or new to the world of mechanical watches, this A–Z glossary will guide you through the language of the craft.
From complications to calibres, these are the terms you should know.
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Mechanical watch terminologies and other horology and watch-keeping words
Analogue A traditional display style using rotating hands on a dial to indicate time.
Automatic A self-winding mechanical watch powered by the motion of the wearer’s wrist.
Balance Wheel The component regulating timekeeping in mechanical watches.
Batman (a slang for a type of Rolex watch)
Rolex GMT-Master II with a black and blue bezel.
Bezel
The ring surrounding the watch face, often used for timing or decoration.
Calibre
The movement or internal mechanism of a watch, often identified by number or name.
Coke (a slang for a type of Rolex watch)
Rolex GMT-Master II with a black and red bezel.
Complication
Any additional feature on a watch beyond standard timekeeping.
Chronograph
A timepiece with stopwatch functionality, operated via pushers.
Crown
A small knob, usually on the right side of the watch case, used to set the time and date or wind a mechanical movement.
Crystal
The transparent cover over the dial, typically made of sapphire, mineral glass, or acrylic. 👉📝 Read our crystal replacement/repair guide!
Cyclops
A small magnifying lens on the crystal, usually positioned over the date window to enhance readability, famously used on Rolex watches.
Dial
The visible face of the watch that displays the time and complications.
Diver’s Watch
A highly water-resistant watch designed for underwater diving, usually featuring a unidirectional bezel.
Escapement
The mechanism that transfers energy from the mainspring to regulate timekeeping.
Flyback
A chronograph function that allows the user to reset and restart with a single press.
Frequency
Measured in vibrations per hour (vph); it determines how smoothly a watch runs.
Gear Train
Series of gears that transmit energy from the mainspring to the escapement.
GMT (Greenwich Mean Time)
A function allowing a watch to display a second time zone, often via an additional hand.
Hands
Pointers that move around the dial to indicate hours, minutes, and seconds.
Horology
The art and science of measuring time and constructing watches.
Hulk (a slang for a type of Rolex watch)
Rolex Submariner with green dial and green bezel (ref. 116610LV).
Indices
Hour markers on a watch dial, ranging from simple lines to numerals.
Incabloc
A common shock protection system in mechanical watch movements.
Jewels
Synthetic rubies used at friction points in a watch movement to reduce wear.
Kinetic
A Seiko technology combining automatic winding and quartz regulation.
Kermit (a slang for a type of Rolex watch)
Rolex Submariner with green bezel and black dial (ref. 16610LV).
Lume
Short for luminescence; glowing material applied to hands and indices for visibility in the dark.
Lug
Protrusions on the watch case used to attach the strap or bracelet.
Mechanical
A watch powered by a mainspring and regulated by an escapement, requiring winding.
Mainspring
A coiled spring that stores energy to power a mechanical watch.
Numerals
The numbers displayed on the watch face, can be Arabic or Roman.
NATO Strap
A one-piece nylon strap that threads through both lugs and under the case.
Open Heart
A dial design that exposes part of the movement, typically the balance wheel.
Oscillator
Part of the movement (usually a balance wheel or quartz crystal) that maintains consistent timing.
Oreo (a slang for a type of Rolex Daytona)
Black ceramic bezel and panda-style white dial, resembling an Oreo cookie (e.g., Daytona ref. 116500LN).
Power Reserve
The length of time a fully wound mechanical watch can run without rewinding.
Panda (a slang for chronograph dial layout)
White dial with black subdials, resembling a panda’s face.
Perpetual Calendar
A complication that displays the correct date, accounting for months and leap years.
Pepsi (a slang for a type of Rolex watch)
GMT-Master II with red and blue bezel, resembling Pepsi branding.
Quartz
A battery-powered movement regulated by a quartz crystal.
Rotor
A weighted disc in an automatic watch that winds the mainspring with wrist movement.
Retrograde
A complication where hands reset to the starting position rather than moving in a circle.
Root Beer (a slang for a type of Rolex GMT)
GMT-Master II with brown and black bezel, often in two-tone or Everose gold.
Skeleton
A watch with visible internal components, either through the dial or caseback.
Subdial
A smaller dial within the main dial that displays additional information such as chronograph or seconds.
Smurf (a slang for a type of Rolex watch)
White gold Submariner with rich blue dial and bezel.
Tourbillon
A rotating cage for the escapement, designed to improve accuracy by counteracting gravity.
Tachymeter
A scale on the bezel or dial used to measure speed based on time.
Unidirectional Bezel
A bezel that rotates in only one direction (usually counterclockwise) for safe timing in diving.
UTC (Coordinated Universal Time)
Time standard used globally, especially in aviation; often used interchangeably with GMT.
Vintage
A term typically used for watches over 20–25 years old.
Vibration
A measure of the oscillation rate of a mechanical movement, often expressed in vph (vibrations per hour).
Water Resistance
The ability of a watch to resist water intrusion at various depths or conditions.
Winding Crown
The knob used to set the time and wind the mainspring on a mechanical watch.
X-Factor* (slang, informal)
Used among collectors to describe a watch’s intangible appeal or standout presence.
Yellow Gold
A classic alloy of gold, often used for watch cases and accents.
Yacht-Master
A Rolex model line designed for sailing enthusiasts, often featuring bidirectional bezels and luxury finishes.
Yacht Timer
A chronograph function used to countdown the start of a yacht race.
Zenith Daytona
Rolex Daytonas made from the late 1980s to 2000 using a modified Zenith El Primero movement.
Zulu Time
Another term for GMT, used commonly in military and aviation contexts.
12-Hour / 24-Hour Dial
Refers to watches that either repeat the time twice daily (12-hour) or display a full 24-hour scale—used in military or GMT watches.
24-Jewel Movement
Describes a movement containing 24 synthetic rubies to reduce friction in the gear train. Jewel counts are often used as a shorthand for quality in mechanical movements.
3H
Seen on military watches, stands for "Tritium Hydrogen" – a luminous material used for glowing hands and indices.
4R36 / 7S26
Seiko movement codes. Widely used in their automatic watches, these numbers often appear on the caseback or spec sheet.
5 Sports
Seiko 5 Sports – a well-known line of affordable automatic watches. The “5” refers to its five hallmark features (automatic, day/date, water resistance, recessed crown, durable case/bracelet).
9F
A legendary high-accuracy quartz movement from Grand Seiko, celebrated for ±10 seconds/year precision.
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A deeper appreciation of timepieces begins with understanding the language that defines them.
Getting familiar with these terms offers you a window into the centuries-old traditions of craftsmanship, innovation, and mechanical excellence.
As you continue exploring or caring for your own collection (or even if you're just getting started!), let this glossary be your guide to reading between the hands and beneath the dial. We hope this glossary is as useful to you as it was for us to compiled and develop.
Did we miss out on any terms in this guide? Drop us a line below to let us know, we’d love to hear from you (we will keep this piece updated with the help of readers like you!).
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