Watch Term Glossary

Altimeter: a function that measures the height, known as altitude, above sea level.

Analog: a watch using both hour and minute hands to display time.

Annual Calendar: a mechanical watch complication that shows the hour, date, day and month.

Authorized Dealer: this is a watch seller who has been officially sanctioned by the watch manufacturer to sell their watch brand. Authorized Dealers have full manufacturer warranties.

Automatic winding movement: in essence, this is the same as a mechanical watch that does not need to be manually wound on a daily basis. In addition, there is a Rotor attached to the back of the watch that is a weighted pendulum that automatically winds the watch.

Balance Spring: a very fine spiral spring in a mechanical watch and sometimes other timekeeping mechanisms that controls the movement and fluctuation of the balance wheel.

Balance Wheel: the weighted wheel in a mechanical watch that oscillates back and forth for the purpose of dividing time into equal segments to keep track of time.

Barrel: a cylindrical box enclosing the mainspring of a mechanical watch, which is the power source for the timepiece. The size of the barrel determines the length of the power reserve for the watch.

Bezel: a revolving rim on a timepiece that either serves to hold the watch crystal in its setting or to measure time increments.

Bi-Directional Rotating Bezel: this type of bezel can be moved both clockwise and counter-clockwise depending on how the wearer wishes to keep track of elapsed time.

Calendar: a function of a watch that displays the correct day or month, and oftentimes the day of week and year.

Caliber: Since the early 18th Century, the specific internal movement of a timepiece has been referred to as caliber. Originally, it was used to illustrate the size and position of a timepiece’s different movements. Today, the term is used to designate a specific model, as different watch manufacturers number their calibers based on their own identification system.

Case: Typically made of metal, this is the part of the watch that varies in size depending on the watch and houses the dial, battery, movement and other internal parts of the watch.

Chronograph: a type of watch that features a stopwatch function, instead of just displaying the current time.

Chronometer: a watch is only given the prestige of being called a chronometer when the official Swiss watch testing facility called the Controle Officiel Suisse des Chronometeres (aka COSC) verifies that the timepiece has met its precision standards. Typically, the COSC measures the performance of the timepiece’s movement at 3 different temperatures in 5 different positions over a period of 15 consecutive days. If a watch passes the COSC’s test, then it becomes a certified chronometer and is given the reputation as keeping extremely accurate time.

Complication: Any function on a watch that goes beyond simple timekeeping, such as displaying hours, minutes and seconds. Common simple complications include: chronographs, alarm, annual calendar and GMT functions. Some more advanced complications include: a perpetual calendar, Tourbillon and minute repeater.

Crown: a round grooved button on outside of the case that is used to wind and set the hands, day and date on a watch so that the watch displays the time and calendar. In addition, it winds the mainspring of the watch.

Crystal: This is the clear cover on the dial, or watch face, that protects the dial by allowing it to be viewed without opening the watch case. It is typically made of glass, plastic, mineral crystal or sapphire crystal to protect the watch face.

Day/Date: a feature of a watch that shows both the day of the week and the date of the month on the watch dial.

Deployant Buckle: an expandable buckle that attaches to one of the sides of the watch strap so that the wearer can easily slip the watch on his/her wrist, set the correct size and snap it shut on the wrist. To elongate the life of the strap, it is best to keep it at the size that is first set to reduce the stress to the strap and preserve its quality.

Dual Time: this type of watch shows the wearer’s local time in addition to at least one other time zone. This is usually shown by the display of a supplemental hour hand which tracks the time based off a 24 hour time mode.

Dial: the face of the watch with hour indicators that shows the time of watch, and other functions depending on the watch’s various complications.

Elapsed Time Rotating Bezel: a rotating bezel that is used to keep track of periods of preset time that has elapsed.

Escapement: the device in a mechanical timekeeping movement that maintains the oscillation of the balance wheel and therefore controls the motion of the hands. In essence, the escapement controls the rate at which the balance wheel and watch hands rotate.

Fly-back Chronograph: a chronograph with a second hand that can be used to time specific activities, such as keeping track of laps completed or the finishing times for competitors in a race. It is known as a fly-back because when it is reset, it is immediately brought back to zero without the need to stop, reset and restart the chronograph.

Function: A watch term that describes the various different tasks and movements a watch is capable of performing, such as a chronograph or calendar.

Gear Train: the gear system that diffuses power from its source at the mainspring of the watch to the escapement, which controls the motion of the watch hands.

GMT Time Zone: Greenwich Mean Time or GMT is the time standard for all other parts of the world besides the United States. This time standard is the same all year round and is not affected by summer time or daylight savings time.

Gold Plating: To enhance the look of a base metal case or bracelet, a layer of gold, or gold plating, is deposited onto the base metal.

Gray Market: when an unauthorized dealer sells new watches and makes a profit.

Guilloche: This is also known as engine turning (see definition). This is the use of engraving to make very intricate and delicate patterns on a material of a watch.

Horology: The science of time measurement that often includes studying time, timepieces, and the art of designing watches.

Jewels: Synthetic gemstones usually made of ruby or sapphires that serve as directors for gear trains in a mechanical watch, reducing friction and wear.

Karat: an indication of the purity of the metal used, expressed in the number of 1/24th of the pure metal used in the alloy. Metals such as gold are too soft in their pure state to use in jewelry so they are typically made into an alloy with other metals for strength. 24K (equal to 24/24ths) is pure metal. 18K is pure metal mixed with 6 parts of other metals.

Luminous: when the hands have a thin coating of “glow in the dark” layer that will illuminate when it is dark so the wearer can tell the time when there an insufficient amount of light.

Lugs: The projections on the watch case that hold the strap or bracelet.

Mainspring: In a mechanical watch, this is the coiled spring that provides the power to drive the movement of the watch.

Manual Wind Movement: This type of movement occurs when the wearer winds the crown in order to wind the mainspring of the barrel, which provides power to the watch. Once a watch is wound, it will remain working for a specified amount of time depending on the type and model of watch (generally 35-45 hours).

Measurement Conversion: a watch function that allows the wearer to use his/her watch to convert one type of measurement into another.

Mechanical Movement: When a watch runs without an outside electrical source, and begins to operate as soon as the mainspring is wound (either manual-winding or via automatic winding).

Minute Repeater: A watch that strikes the hours, quarters and minutes on a gong, thus making sounds.

Moon-phase: A window on a watch face that indicates the current phase of the moon, using the moon cycle of 29 ½ days.

Movement: The inner mechanics and motor of a watch that keeps time and allows the watch’s hands to perform functions, such as calendar display. Movements can be either mechanical or quartz, depending on the watch construction.

Perpetual Calendar: An advanced complication that shows the date, day, month and leap year cycle at the minimum.

Platinum: Considered to be one of the rarest and most durable of precious metals.

Power Reserve Indicator: A feature on the mechanical watch that indicates how much longer the watch will operate before it runs down and needs to be wound again.

Quartz Movement: This movement causes the watch to be electronically operated, as the watch contains a quartz crystal that rotates and emits electricity when mechanical pressure is applied to it.

Rotating Bezel: When the ring, or bezel, surrounding the watch face can be turned. In an automatic watch, a rotating bezel is the rotating part that winds the mainspring and generates power.

Rotor Automatic: The special weight in an automatic watch that rotates based on the activity and movement of the wearer of the watch, and this rotation winds the mainspring. Today, this is the most common type of an automatic watch and arguably the only kind that is still manufactured today.

Second Time Zone Indicator: When there is an additional dial on the face of the watch that can be set to the time of another time zone.

Skeleton Case: This type of case if transparent on either the front or the back of the watch case in order to allow visibility of the watch’s various movements and functions.

Stainless Steel: An extremely durable metal alloy that is almost rust and stain resistant; thus, it rarely corrodes or discolors making it a preferential material for a watch case and bracelets.

Subsidiary Dial (Sub Dial): Used to indicate the date, power reserve or elapsed time in a small sub-dial on the watch face.

Superlative Chronometer: This refers to a Rolex chronometer. The use of the word Superlative in front of chronometer is a Rolex trademark to give more flair to their product. However, there is only one grade of chronometer so the terms ‘Superlative Chronometer’ and ‘Certified Chronometer’ and ‘Chronometer’ all mean the exact same thing.

Swiss-Made: A watch can only show the Swiss-Made label if the assembly work of the movement and watch was started, adjusted and controlled by a Swiss manufacturer.

Tourbillon: A device in a mechanical watch that mounts the escapement and balance on a rotating platform cage to eliminate positional timekeeping errors.

Uni-Directional Rotating Bezel: A bezel that monitors elapsed time and only moves in one direction. Oftentimes, this type of bezel is used in diving watches to prevent the diver from overestimating remaining air supply and running out of air if the bezel is accidentally moved from the original position.

Waterproof: This term is no longer used because it implies the watches can be completely resistant to water entry for infinite periods of time.

Water Resistant: This term accurately designates a watch that has passed tests and successfully resists entry of water into its case.

Winding: This action tightens the mainspring of the watch either manually by means of a crown or automatically by a rotor.

World Time Complication: An advanced complication that can tell the time of up to all 24 of the time zones around the world.