A
Automatic
A mechanical watch that winds itself using a weighted rotor that spins as you move your wrist. Also called "self-winding." No battery required—just wear it regularly to keep it running.
Annual Calendar
A complication that automatically accounts for months with 30 and 31 days, requiring manual adjustment only once per year (at the end of February).
Anti-Magnetic
A watch designed to resist magnetic fields that can affect accuracy. Modern standards like METAS require resistance to 15,000 gauss.
Applied Indices
Hour markers that are separate metal pieces attached to the dial, rather than printed. Considered higher quality than printed indices.
B
Balance Wheel
The oscillating wheel in a mechanical watch that regulates timekeeping. It beats back and forth at a consistent rate, typically 6-10 times per second (21,600-36,000 vph).
Bezel
The ring surrounding the watch crystal. Can be fixed, rotating (diving/GMT), or decorative (fluted, gem-set). Dive watch bezels rotate in one direction to time dives.
Bracelet
A metal band attached to the watch. Common styles include Oyster (flat links), Jubilee (rounded links), and mesh (woven metal).
C
Caliber
The specific movement inside a watch, identified by a reference number. "In-house" calibers are made by the watch brand; others use movements from suppliers like ETA or Sellita.
Case Back
The back cover of the watch case. Can be solid, exhibition (transparent), or screw-down (for water resistance).
Chronograph
A watch with stopwatch functionality. Pushers start/stop/reset timing, while subdials show elapsed time. The main timekeeping function operates independently.
Chronometer
A watch that has been tested and certified for accuracy by an official body like COSC. Not all accurate watches are chronometers—it's a specific certification.
Complication
Any function beyond basic timekeeping: date, chronograph, moonphase, GMT, etc. "Grand complications" include minute repeaters, perpetual calendars, and tourbillons.
Crown
The knob on the side of the watch used to set time and date. On diving watches, it screws down for water resistance.
Crystal
The transparent cover over the dial. Types include sapphire (scratch-resistant, most common in luxury), mineral (less scratch-resistant), and acrylic/hesalite (softer but buffs out easily).
D
Date Window
An aperture showing the date, typically at 3, 6, or 12 o'clock. May include a magnifying "cyclops" lens.
Deployment Clasp
A folding clasp that keeps the strap in a loop when open, preventing drops. More secure and easier on leather than a traditional buckle.
Dial
The face of the watch displaying time. Can feature sunburst, guilloché, enamel, mother-of-pearl, or other finishes.
E
Escapement
The mechanism that controls energy release from the mainspring to the balance wheel, creating the "tick" of a mechanical watch.
Exhibition Case Back
A transparent case back (usually sapphire) that allows viewing the movement. Common in dress watches to showcase finishing.
G
GMT
Greenwich Mean Time. A GMT watch has an additional hour hand completing one rotation in 24 hours, allowing you to track a second time zone.
Guilloché
A decorative pattern of interlocking curved lines engraved on a dial. Traditional guilloché is hand-engraved on a rose engine.
H
Hacking
A feature where the second hand stops when you pull out the crown, allowing precise time-setting. Standard on most modern mechanical watches.
Hand-Wound / Manual
A mechanical watch wound by hand via the crown, without an automatic rotor. Many enthusiasts prefer the ritual of daily winding.
Haute Horlogerie
"High watchmaking" — watches featuring exceptional craftsmanship, complications, and hand-finishing. Think Patek Philippe, A. Lange & Söhne, Vacheron Constantin.
L
Lugs
The projections on the case where the strap/bracelet attaches. Lug-to-lug distance determines how large a watch wears on your wrist.
Lume / Luminous
Material applied to hands and indices that glows in the dark. Modern watches use Super-LumiNova; vintage pieces may have radium or tritium.
M
Mainspring
The coiled spring that stores energy in a mechanical watch. When wound (manually or automatically), it slowly unwinds to power the movement.
Manufacture
A watch company that makes its own movements in-house, rather than buying from suppliers. Rolex, Patek Philippe, and Grand Seiko are manufactures.
Moonphase
A complication showing the current phase of the moon through an aperture. Typically accurate to one day every 2-3 years.
Movement
The mechanism inside a watch that makes it work. Types: mechanical (automatic or manual), quartz (battery-powered), and hybrid (Spring Drive, etc.).
P
Perpetual Calendar
A complication that automatically adjusts for all month lengths and leap years. No adjustment needed until 2100 (when the leap year is skipped).
Power Reserve
How long a mechanical watch will run after being fully wound. Typically 40-80 hours; some reach 7+ days. May be shown via an indicator on the dial.
Pusher
A button on the case, typically used to operate chronograph functions (start/stop/reset).
R
Rotor
The weighted semicircular disc in an automatic watch that spins with wrist movement to wind the mainspring.
S
Sapphire Crystal
Synthetic sapphire used as the watch crystal. Extremely scratch-resistant (9 on Mohs scale), but can shatter on impact.
Skeleton
A watch where the dial and/or movement are cut away to reveal the internal mechanism. Visually striking but sometimes harder to read.
Small Seconds
A seconds display on a subdial rather than a center-mounted hand. Traditional on dress watches and vintage pieces.
Spring Drive
Grand Seiko's unique movement combining mechanical power with electronic regulation. Offers the smooth sweep of mechanical with quartz-level accuracy.
T
Tachymeter
A scale on the bezel or dial used to calculate speed based on time traveled. Common on racing chronographs.
Tourbillon
A rotating cage that holds the escapement, designed to average out positional errors. Originally for pocket watches; now mostly a showcase of craftsmanship.
W
Water Resistance
The depth rating a watch can theoretically withstand. Measured in meters, bar (ATM), or feet. Note: ratings are for static pressure; real-world diving involves additional forces.