Horology Glossary
Essential terminology for understanding luxury watches and the art of horology.
Automatic
A self-winding mechanical movement that winds via a rotor spinning from wrist motion. Also called 'self-winding.'
Bezel
The ring surrounding the crystal. Can be fixed, rotating (diving), or bi-directional (GMT). Often features time scales or tachymeters.
Caliber
The specific movement design, identified by a manufacturer's reference number (e.g., Rolex Caliber 3235).
Chronograph
A watch with stopwatch functionality, typically with subdials for elapsed seconds, minutes, and hours.
Chronometer
A precision-certified timepiece tested by COSC (Contrôle Officiel Suisse des Chronomètres) meeting accuracy standards of -4/+6 seconds per day.
Complication
Any function beyond hours, minutes, and seconds. Includes date, moonphase, chronograph, perpetual calendar, minute repeater, and tourbillon.
Crown
The knob on the case side used to wind the movement and set time/date. Often features brand logos or cabochon stones.
Crystal
The transparent cover over the dial. Materials include sapphire (scratch-resistant), hesalite/acrylic (flexible, vintage character), or mineral glass.
Escapement
The mechanism controlling energy release from the mainspring. Types include lever, co-axial, and silicon escapements.
Flyback
A chronograph feature allowing instant reset and restart with a single push, without stopping and resetting separately.
Geneva Seal
A quality hallmark for movements assembled in the Canton of Geneva, requiring hand finishing and specific quality standards.
GMT
A watch displaying a second time zone, typically with a fourth hand and 24-hour bezel. Named after Greenwich Mean Time.
Guilloché
A decorative engraving technique creating intricate, repetitive patterns on dials. Associated with brands like Breguet.
Haute Horlogerie
High watchmaking: exceptional craftsmanship, complex complications, and hand finishing. The pinnacle of the watchmaking art.
In-House Movement
A caliber designed and manufactured by the watch brand itself, rather than sourced from external suppliers like ETA or Sellita.
Luminous Material
Glow-in-the-dark compound on hands and indices. Modern materials include Super-LumiNova and Chromalight.
Mainspring
The coiled spring that stores energy in a mechanical watch. Unwinds slowly to power the movement.
Manufacture
A company producing movements in-house. True manufactures control the entire production process.
Minute Repeater
A complication that chimes the time audibly when activated. One of the most complex and prestigious complications.
Moonphase
A complication displaying the lunar cycle through a rotating disc visible through an aperture.
Movement
The mechanism inside the watch. Types: mechanical (hand-wound), automatic (self-winding), or quartz (battery-powered).
Perpetual Calendar
A complication automatically adjusting for months of varying lengths and leap years, requiring no correction until 2100.
Power Reserve
The duration a mechanical watch runs when fully wound. Typically 40–70 hours for modern movements.
Reference Number
The manufacturer's model identifier combining case, dial, and movement specifications.
Rotor
The oscillating weight in an automatic movement that winds the mainspring via wrist motion.
Sapphire Crystal
Synthetic sapphire used for watch crystals. Extremely scratch-resistant (9 on Mohs scale), second only to diamond.
Skeleton
A movement or dial cut away to reveal internal components, showcasing the mechanical artistry.
Tachymeter
A scale on the bezel or dial used to calculate speed based on time over a known distance.
Tourbillon
A rotating cage housing the escapement, designed to counter gravity's effect on accuracy. A prestigious complication.
Water Resistance
The depth rating indicating water exposure tolerance. Measured in meters, bar, or ATM. Requires regular gasket maintenance.