Watch Glossary

ATM: Measures water resistance; Stands for "atmospheres" or the amount of pressure a watch can withstand before leaking; One atmosphere is equal to 10 meters of water pressure.

Bezel: Retaining ring topping the case and securing the crystal; Sometimes incorporates unidirectional or ratcheting movements, engraved or printed chapter markers, or complications such as a tachymeter.

Chronometer: High-precision timepiece that has been tested and is certified to meet precision standards; Chronometer watches often come with certificates indicating their certified status.

Complication: Any feature added to the timepiece that does not indicate hours, minutes or seconds.

COSC Certified Chronometer: Refers to timepieces that have been christened with the title of chronometer. To become a chronometer, timepieces have to pass a test conducted by the Controle Officiel Suisse des Chronometers (COSC), roughly translating to Official Swiss Chronometer Testing Institute. COSC is a prestigious Swiss government agency that certifies the accuracy and precision of timepieces in Switzerland.

Crown: Part that allows you to manipulate the watch movement for a variety of purposes such as setting the hands, changing the date, winding the mainspring, etc.

Crystal: Transparent cover on a watch face that gives view of the dial.

Deployant: Type of clasp that keeps the closing mechanism hidden, creating an uninterrupted look for your bracelet or strap.

Dual Time Zone: Timepiece that simultaneously gives time in two time zones. GMT function serves the same purpose and is used interchangeably, as it can be set to any time zone you wish.

Exhibition Case or Back: Unique complication wherein a crystal window is implemented into the back of a watch case, allowing view of the timepiece's movement.

Function Pushers: Manual controls on a case for when a movement features complications that require increased manipulation.

Greenwich Mean Time (GMT): Also referred to as Greenwich Meridian Time, the Greenwich Meridian Line is located at the Royal Observatory in Greenwich, England. It is the place from where all time zones are measured. Greenwich Mean Time is the average time that Earth takes to rotate from noon to noon. In this regard, GMT is thought of as "the world's time" and was once the basis with which every other zone set time.

Guilloche: Style of engraving that features wavy or straight lines, giving a unique effect when the timepiece is moved or shifted.

Ionic Plating: Process that produces a hardened surface that is durable and scratch-resistant; Has a black flat "stealth" finish.

Jewels: Within a movement, metal on metal contact creates wear and tear. Watchmakers use jewel bearings to reduce friction and help the delicate parts of the movement work smoothly and with great precision. Jewels help extend the movement's life. Diamonds, sapphires, rubies and garnets are the preferred materials. As a general rule, a higher number of jewels suggests a more prestigious movement.

Lugs: North and south ends of the case that attach to the strap or bracelet and often extend out from the dominant lines of the case.

Moon Phase: The lunar cycle has been a cornerstone of horology, the study of measuring time, since ancient days. Moon Phase is a complication on a timepiece that displays the various stages of the moon cycles from waxing to waning. It appears as a dial visible through an aperture which reveals the current moon phase.

Movement: Assembly making up the principal elements and mechanisms of a watch or clock; Includes the winding and setting mechanism, the mainspring, the train, the escapement and the regulating elements.

Power Reserve: Time a watch will continue running based on the movement's residual winding of its mainspring; In quartz and digital watches, this can also refer to the amount of energy left in the battery.

Push Button Dual Deployant: Similar to deployant and considered one of the most desirable and easy-to-use clasps, the push button dual deployant employs two small hidden push buttons that release the bracelet. This clasp keeps the closing mechanism hidden for an uninterrupted, seamless finish.

Repeater: Complex watch mechanism that sounds hours, quarters or minutes, or repeats them on request; Originally designed to help the wearer to tell the time in the dark.

Retrograde: Hour, minute, second or calendar hand that moves across a scale and resets to zero at the end of its cycle.

Skeletonization: Reveals the intricate symphony of moving rotors, gears and springs which power a timepiece; The open design offers an insider's view, as unnecessary metal is cut away to allow the wearer to actually see the movement's skeleton.

Swiss Made: Since the 16th century, Switzerland has been the epicenter of watch making, producing some of the industry's greatest technological advances. The Swiss put a law into effect for all timepieces baring the words "Swiss Made": First, the movement must be assembled in Switzerland. Secondly, the movement must be cased up in Switzerland. Finally, the manufacturer must carry out the timepiece's final inspection in Switzerland.

Tachymeter: Scale on a watch used to determine units per hour, such as average speed over a fixed distance, or distance based on speed; Typically located along the outer rim of a dial.

Tritium: Miniature tubes containing gaseous Tritium and layered with phosphor to power the luminous accents which can be seen for several meters in darkness. Tritium illumination requires no electrical power but must be "charged" by holding your watch close to any light source. The longer you hold it there, the longer and brighter you'll see the Tritnite.

Unidirectional Rotating Bezel: Used for tracking elapsed time. A ratchet mechanism prevents the bezel from rotating backwards. This feature is popular with divers, who rely on the elapsed time feature to prevent the diver from running out of air. The fact that the bezel cannot rotate backwards prevents the wearer from underestimating the elapsed time.

Chronograph: Functioning similarly to a stopwatch, a chronograph is a unique and valued complication due to its ability to measure increments of elapsed time while the watch still maintains traditional timekeeping abilities. The crown controls the analog watch while function pushers allow you to start, stop and reset the chronograph subdials. Variations of chronographs include the double chronograph with two separate stopwatch mechanisms and the flyback chronograph which allows the user to stop, reset and start the chronograph with a single depression of the function pusher.

Quartz: Although not as mechanically complex as other engines, the quartz movement provides the most accurate and reliable time-keeping. This type of movement typically draws power from a battery and centers around a small vibrating chip of quartz crystal. When an electrical current, supplied from a battery, is applied to a quartz crystal, the current is distorted and creates a precise resonating frequency. Watchmakers employ the subsequent frequency to measure time. Some adaptations to the traditional quartz movement include introducing rotors and power cells in an effort to maintain the accuracy of quartz while eliminating the need for a battery. Quartz movements have been used in timepieces since the 1970s and are highly accurate, dependable and affordable.

The case provides the foundation for all other major watch components. It houses the movement, maintains the lugs for attachment to the bracelet or strap, plays host to various crowns and function pushers, and seats the crystal and bezel.

Cases exist in a variety of shapes and sizes and utilize a library of materials for construction such as stainless steel, gold, ceramic, titanium, plastic, and more. The dominance of stainless steel in case construction remains, however, hypo-allergenic metals and materials, like titanium, continue to gain in popularity. Metal cases often have particular finishes - such as a smooth reflective polish or circular matte brush - that enhance the presentation of the timepiece and give it unique depth.

Some designs allow for the case and lugs to be curved in order for the watch to have a more comfortable fit around the wrist. The back of a case will typically be removable and most likely be screw down or pop-off. It is important to note, however, it should only be opened by a trained professional. An exhibition feature (found within a case's back) refers to an added window that allows you to view the movement and is often found on automatic and mechanical timepieces.

Case Size:
Case measurements do not include crown or lugs.

Round - One measurement, 8:00 to 2:00
Square - One measurement, 3:00 to 9:00 or 6:00 to 12:00 (should be the same)
Rectangle, Tonneau, Oval, Octagon, etc. - Two measurements, 3:00 to 9:00 and 6:00 to 12:00

Watch Case Dimension Comparisons:
It can be difficult to determine how a watch will fit on your wrist without trying it on first. Get a better feel for the size of a watch case by comparing the case diameter to the following diameters of common objects:

Nickel: 21.21mm
Quarter: 24.26mm
Half Dollar: 30.61mm
Poker Chip (standard): 39mm
Ping Pong Ball: 40mm
Golf Ball: 42.67mm
Tow Ball Hitch (ISO standard): 50mm
Racquetball: 57mm
Soda Can (standard): 65mm
Tennis Ball: 67mm

The case provides the foundation for all other major watch components. It houses the movement, maintains the lugs for attachment to the bracelet or strap, plays host to various crowns and function pushers, and seats the crystal and bezel.
Cases exist in a variety of shapes and sizes and utilize a library of materials for construction such as stainless steel, gold, ceramic, titanium, plastic, and more. The dominance of stainless steel in case construction remains, however, hypo-allergenic metals and materials, like titanium, continue to gain in popularity. Metal cases often have particular finishes - such as a smooth reflective polish or circular matte brush - that enhance the presentation of the timepiece and give it unique depth.
Some designs allow for the case and lugs to be curved in order for the watch to have a more comfortable fit around the wrist. The back of a case will typically be removable and most likely be screw down or pop-off. It is important to note, however, it should only be opened by a trained professional. An exhibition feature (found within a case's back) refers to an added window that allows you to view the movement and is often found on automatic and mechanical timepieces.
Case Size:
Case measurements do not include crown or lugs.
Round - One measurement, 8:00 to 2:00
Square - One measurement, 3:00 to 9:00 or 6:00 to 12:00 (should be the same)
Rectangle, Tonneau, Oval, Octagon, etc. - Two measurements, 3:00 to 9:00 and 6:00 to 12:00