The world of watches comes with its own set of terminology. While some of these terms are self-explanatory, others aren’t. We get it, so we’ve compiled this watch glossary so you can better understand some of the jargon you’ll come across when reading about timekeeping, horology, and luxury watches. Don’t forget to bookmark this page so you can refer to it anytime you need a watch definition.
A
Alarm
A mechanism that makes a sound at a predetermined time.
Altimeter
An instrument that measures altitude.
AM/PM indicator
An indicator on a 12-hour display that shows whether it’s nighttime or daytime, which is traditionally expressed via a sun or moon icon. An AM/PM indicator is also known as a Day/Night indicator.
Analog watch
A watch that indicates the time via hands on a dial.
Aperture
A small window on a dial. Typically refers to a calendar window that displays the date, day, month, or moon phase.
Annual calendar
An annual calendar is a watch complication that differentiates between months with 30 and 31 days. Therefore, it only has to be manually adjusted once a year, when February turns into March.
Learn more: What is an Annual Calendar Watch?
Anti-magnetic
A watch built to withstand the detrimental effects of magnetic fields.
ATM
Unit used to measure atmospheric pressure. Used in watches to denote water resistance where 1 ATM equals 10 meters or 1 bar.
Automatic movement
A type of mechanical watch movement that relies on the motion of a wrist to move the rotor back and forth to wind the mainspring. If left motionless too long, an automatic movement will stop working until it’s wound up again. Also referred to as a self-winding movement.
Automatic watch
A watch powered by an automatic mechanical movement.
B
Balance spring
A tiny spring that returns the balance wheel back to its neutral position. Also referred to as a hairspring.
Balance wheel
The timekeeping mechanism in a movement that oscillates. The balance spring and balance wheel work together to regulate the movement, similar to a clock pendulum. Each swing of the balance wheel creates a beat that advances the gears, which then drives the hands forward on the dial.
Band
A watch strap that can be made from leather, fabric, or rubber, and secures the watch to a wrist.
Barrel
A round box inside a mechanical movement that houses the mainspring. Usually, the larger the barrel, the more power reserve a movement has.
Beats per hour (bph) aka Vibrations per hour (vph)
The number of vibrations/ticks/beats per hour of a watch. High-end watches typically boast quicker frequency rates such as 21,600 bph (6 ticks/second), 28,800 bph (8 ticks/second), or 36,000 bph (10 ticks/second). The faster the ticking of a watch the more precise it is.
Bezel
The ring on top of the case that frames the dial, which secures the crystal in place. Some bezels are decorative while others are functional. Most functional bezels will include a scale (for example 24-hour, 60-minute, or tachymeter) and some will rotate too.
Bracelet
A metal watch strap, usually made in the same material as the case, that secures the watch to a wrist. Learn more about watch bracelets.
Bridge
Series of plates or bars that hold components of the watch movement together. Bridges are attached to the mainplate with screws.
C
Cabochon
A polished stone, typically mounted onto a winding crown for decorative effect.
Calendar
A watch function that indicates the date, day, month, and/or year.
Caliber
Another name for a watch movement, which is the mechanism that powers the watch.
Case
The main portion of the watch that houses the movement and dial. Watch cases are available in a range of shapes, sizes, and materials.
Learn more about watch cases:
An Introduction to Common Materials Used in Watchmaking
A Primer on Watch Case Shapes
Watch Size Guide: Does Size Really Matter?
Caseback
The back of a watch case (opposite of the dial side) that sits on the wrist. Casebacks can be snap-in or screw-down. They can be solid metal or include a crystal window for a view of the movement inside the case.
Chronograph
A watch function that can measure elapsed times via a start, stop, and reset mechanism — also known as a stopwatch. Modern chronograph watches generally measure time via a central chronograph hand, which is activated by two chronograph pushers on the case. Chronographs also typically have minute and hour counters on the dial.
Learn more: What is a Chronograph?
Chronometer
A highly precise watch that comes with an official certification. Swiss-made chronometers are certified by Contrôle Officiel Suisse des Chronomètres, better known as COSC.
Cloisonné
A decorative technique where materials, such as enamel, glass, or gems, are separated by thin strips of metal. Cloisonné dials are reserved for ultra-high-end watches.
Complication
Any additional function on a watch that goes beyond telling the time. For instance, perpetual calendar, chronograph, moon phase, minute repeater, and world timers are all watch complications. A grand complication is a watch that combines several complications.
COSC
Contrôle Officiel Suisse des Chronomètres, the institute responsible for testing and certifying the precision and accuracy of Swiss chronometers.
Côtes de Genève
A special type of striped finishing used to decorate high-end movements. Côtes de Genève is also known as the Geneva Stripes.
Crown
A button positioned on the outside of the case that serves to primarily wind the movement and set the time (and other functions, if applicable). Also known as the winding crown or winding stem.
Crystal
The clear component covering the dial, typically made from acrylic, glass, or synthetic sapphire. Most luxury watches today use sapphire crystals, which are prized for their resistance to scratching and shattering.
D
Day-Date
A watch function that indicates the day of the week along with the date of the month.
Deployant clasp
A type of folding metal buckle used on watch bands and bracelets. Deployant clasps provide more security than a typical tang buckle.
Depth alarm
A mechanism that makes a sound when a dive watch submerges below a certain depth.
Dial
The face of the watch that houses the watch hands, indexes, and/or functions. Dials can be made in a range of materials, colors, and styles.
More on watch dials: Every Special Rolex Dial
Digital watch
A watch that displays the time using digits on a screen, typically LCD.
Dual Time
A watch that indicates two time zones simultaneously. A GMT watch is a specific type of dual time watch that indicates the second time zone on a 24-hour scale instead of a 12-hour scale.
E
Ébauche
An unassembled movement kit that can be built, modified and/or branded by different watch companies. The most Swiss famous ébauche movement maker is ETA, and these ETA movements are the base for many luxury watch movements.
Enamel
An opaque glassy substance applied to metal surfaces, typically used as a decorative element on dials of high-end watches.
Engine-turned
A decorative technique of repetitive patterns engraved into metal surfaces. Also known as guilloché.
Equation of time
A watch complication that displays the disparity between mean solar time and true (apparent) solar time.
Escapement
A mechanism inside a watch movement that controls the energy from a power source (i.e. the mainspring) and transforms it into lateral impulses. The escapement has a pallet fork that locks and unlocks with the escape wheel at each vibration of the balance wheel. Without an escapement, the mainspring would uncoil immediately, releasing all its energy at once.
F
Flyback chronograph
A special type of chronograph complication whereby the central chronograph hand can be reset without having to be stopped first.
Frequency
The number of vibrations (or beats) per hour expressed in hertz (Hz). For example, a 4Hz (28,800 bhp) movement or a 5Hz (36,000 bph) movement.
G
Gasket
Rubber rings that create airtight seals around case openings (such as the caseback, crystal, and crown) to improve water resistance. Gaskets have to be replaced every few years to ensure the watch is still water-resistant.
Gear train
A mechanical system of mounted gears that transfers energy from the mainspring to the escapement.
Grand Prix d’Horlogerie de Genève (GPHG)
An annual awards ceremony in Geneva, Switzerland, that gives awards to the best watches across several categories. The top prize is the “Aiguille d’Or,” which is awarded to the very best watch of the year.
Grande sonnerie
A complication that combines quarter striking and minute repeater complications. At every quarter hour, it sounds the hours and quarters on two gongs. It can also strike the hours on demand via a button.
Greenwich Mean Time (GMT)
Previously used as the international civil time standard but now replaced by Coordinated Universal Time (UTC). GMT watches are a special type of dual time watch that indicate the second time zone on a 24-hour scale.
Learn more: What is a GMT Watch?
H
Hacking seconds
A mechanism that halts the seconds hand when the crown is pulled out for precise time setting or synchronization.
Hands
The indicators that rotate around the dial to point to the hour, minute, second or any other indicator. Hands come in a range of shapes and sizes.
Haute Horlogerie
The French term that translates to “high watchmaking” or “high horology.” The Haute Horlogerie label is generally reserved for the finest mechanical watches that run on complex complications and are embellished with traditional decorative techniques.
Helium escape valve (HEV)
A mechanism that automatically expels any gasses from the watch that can build up in pressurized environments. Helium escape valves are normally found on saturation dive watches.
Horology
The science of measuring time or the art of making timekeeping instruments.
Hour markers
The indexes around the dial that indicate the hours. Hour markers are available in a wide assortment of styles, ranging from numerals to sticks to shapes.
I
Integrated bracelet
A style of bracelet that is incorporated into the watch case. Integrated bracelets were a trend that started in the 1970s and a popular style with luxury sports watches.
J
Jewels
In watch movements, jewels refer to synthetic rubies used as bearings in gears to reduce friction. They are set into the drilled holes of plates and bridges.
Jump hour
A hand that jumps to the hour every 60 minutes instead of slowly edging towards it over the course of the hour. Sometimes, rather than a hand, a jump hour watch will include a window with numerals.
K
Karat
A measurement indicating the proportion of gold in an alloy out of 24 parts. For example, 18k gold is 18/24 parts gold, or 75 per cent gold. While many vintage watches were made in 9k or 14k gold, high-end watch brands today only use 18k gold.
Keyless works
Gears that not only wind the mainspring via the turning of the winding crown but also allow the hands to be set when the crown is pulled out. Named so because prior to this invention, keys had to be used to wind the movement.
L
Lacquer
A hard protective coating for a range of materials. Originally made from the sap of a lacquer tree, there are synthetic substitutes today. Sometimes found as a decorative technique on the dials of high-end watches.
Lever escapement
A type of escapement that includes a forked lever positioned between the escape wheel and the balance that locks and unlocks the escape wheel teeth.
Lugs
The protrusions on a watch case that holds a spring bar. The spring bar is what attaches the watch band, strap, or bracelet to the case.
Luminescence
A substance applied to the face so a watch glows in the dark. Also known as watch lume, different materials have been used as luminescence on watches, including highly radioactive radium and less radioactive tritium, both of which are self-luminous. Modern watches now generally use photoluminescence, which requires a “charge” (exposing the material to light first) before it can glow in the dark.
M
Mainspring
The spring inside a movement that has to be wound to supply power to the watch.
Manual winding movement
A mechanical movement that requires the user to wind the crown to wind the mainspring. Manual winding movements are also known as hand-wound movements.
Manufacture
The French word for manufacturer that is generally used interchangeably with “watch brand” or “watch company.”
Marine chronometer
A precise timepiece that was used on a ship to calculate position by celestial navigation. The marine chronometer was invented in the 1700s by British clockmaker, John Harrison.
Mechanical watch
A traditional type of watch that doesn’t require electricity to operate. A mechanical watch sources its power from a wound mainspring. The two types of mechanical watches are automatic watches and manual winding watches
Moon phase
A watch complication that indicates the phases of the moon on the dial.
Mother-of-pearl
Also known as nacre, mother-of-pearl (MOP) is the outer layer of a pearl or the inner layer of a shell that is sometimes used on the dials of luxury watches.
Movement
The mechanism that powers the watch. There are quartz movements powered by batteries and mechanical movements powered by a wound mainspring. Mechanical movements can be self-winding or manual-winding.
O, P, Q
Oscillation
Also known as swing, oscillation is movement back and forth at a regular speed. For instance, each oscillation of a pendulum represents one second.
Perpetual calendar
A watch that correctly indicates the time, day, date, month, and leap year (often moon phase too) in perpetuity without the need for adjustment. The only time a perpetual calendar will need manual adjusting is in the year 2100 when, according to the Gregorian calendar, the leap year will be ignored.
Learn more: What is a Perpetual Calendar Watch?
Physical vapor deposition (PVD)
A thin coating applied to a watch case and/or bracelet to add color. Black PVD watches have been especially popular in recent years.
Power reserve
The amount of energy that can be stored in a watch before the mainspring needs to be wound again. A power reserve indicator is sometimes placed on a dial of a watch.
Pusher
A button on a watch case that is pressed to activate a specific function. For example, there are chronograph pushers, alarm pushers, striking pushers, among others.
Quartz movement
A movement that has a quartz crystal, which oscillates at a very precise frequency to regulate timekeeping. A quartz movement does not require winding and sources its power from a battery. Sometimes, the battery can be recharged via solar power or kinetic energy.
Learn more: Rolex Quartz Watches: The Complete Guide
Quick-set
A feature that allows a calendar indication (such as date, day, month, and so on) to be set independently from the timekeeping hands.
R, S
Rattrapante
A special type of chronograph watch that includes two chronograph hands to measure two events that start at the same time but end at different times. A rattrapante is also known as a split-seconds chronograph.
Repeater
A watch complication that chimes the time using bells and gongs. There are several types of repeaters including quarter-repeaters (that chime the hours and quarters) and minute repeaters (that chime the hours, quarters, and minutes). Repeater watches were invented as a way to tell the time in the dark before electricity was invented.
Learn more: What is a Minute Repeater Watch?
Retrograde
A complication that includes a hand that moves over a portion of an arc then jumps back to the start when it gets to the end of the arc. A retrograde display can indicate the day, date, hours, minutes, and/or seconds.
Rotor
The mechanism in an automatic movement that swings back and forth (thanks to the natural motion of the wrist) that serves to wind the mainspring.
Skeleton watch
A watch with a face that is designed to show as much of the movement as possible. Skeleton watches are sometimes called open-worked watches.
Slide rule
An analog calculation tool that pre-dates digital calculators. Pilot watches can have circular slide rules on the bezel to assist in calculating fuel consumption, airspeed, and distances.
Small seconds indicator
A subsidiary dial on the face of the watch that indicates the seconds. The small seconds indicator (also known as small seconds) replaces the traditional center seconds hand.
Subsidiary dials
Smaller dials on the main watch dial, which are used to display various indications including seconds, calendars, second time zones, chronographs, and so on. Subsidiary dials are sometimes called subdials, counters, or registers.
T, W
Tachymeter
A scale often found on the bezels of chronograph watches that can measure speed or distance.
Telemeter
A scale sometimes found on a watch used to determine distance based on time.
Tourbillon
A mechanism invented by Abraham Louis Breguet to offset the detrimental effects of gravity on a watch movement. A tourbillon constantly rotates the balance wheel, balance spring, and escapement in a cage, often right on the dial for all to see.
Water resistance
The rating of how much water pressure a watch can withstand, indicated in meters, feet, ATM, or bars. In some countries, the term “waterproof” is illegal as no watch can claim to be 100% waterproof.
Wheels
Large gears made of brass that make up the gear train. The gear train transfers energy from the mainspring to the escapement. Pinions are small gears made of steel.
Winding
The action of winding the mainspring to power a mechanical watch. This can be done manually via the crown or automatically via a rotor that swings back and forth with the natural motion of a wrist.
World Time
A watch complication that permits the simultaneous indication of 24 time zones. A world time watch typically has a ring on the dial periphery with 24 major cities to represent each time zone.