Alarm: A watch function that gives a signal (sound or vibration) at a pre-set time.
Altimeter: An altimeter determines altitude, by reacting on barometric pressure. This device records ascent and descent, providing very useful information for explorers, climbers, aviators…
AM/PM Indicator: See Day/Night Indicator
Analog Display: An interface that displays time by hands and a dial.
Analog Watch: A timepiece with a dial, hands, and numbers or indexes that form 12 (or 24) hours.
Annual Calendar: A date indicator, adjusted for short and long months (except for 29 February).
Aperture: A small opening (window) on a dial.
Auto Repeat Countdown Timer: When the preset time has elapsed, a timer immediately resets itself and repeats to countdown time until it is stopped manually. See Countdown Timer
Automatic Movement: A mechanical movement that requires no winding (when a watch is in motion), thanks to a rotor that winds the mainspring with every movement of a hand. However, when a watch is not worn, most automatic mechanisms use a certain power-reserve (up to 36 hours) before they stop working. In order to start beating again, they need to be manually wound 30-40 times. Abraham-Louis Perrelet fromSwitzerland invented a self-winding movement in the 18th century.
Balance Spring: It is also known as a “hair spring”. This very fine spring in a mechanical timepiece puts the balance wheel back to a neutral position, which regulates a timekeeping.
Balance Wheel: A part of a mechanism that oscillates, and splits time into equal segments, which provides accuracy.
Barrel: Thin cylindrical box closed by a cover, with a ring of gear teeth around it. It contains the mainspring of a watch. Its toothed rim engages the wheel train of a watch, usually the central wheel. The size of a barrel has direct impact on a power-reserve. Some timepieces incorporate two barrels, which provides the high level of a power-reserve.
Bezel: A ring that surrounds a watch dial. A Bezel can be used for measuring time increments or even speed (if it features a tachymeter scale). It is either rotatable (uni-directional, bi-directional turning bezel) or fixed.
Bi-directional Rotating Bezel: A bezel that can be turned either way (clockwise or counterclockwise). It is used for calculating elapsed time, by aligning the bezel’s #12 at the beginning point, or for mathematical calculations.
Bracelet: A type of a watch band, made up of separate links.
Bridge: A complementary part fixed to the main plate to form the frame of a watch movement. The other parts are mounted inside the frame.
Calendar: A feature that display a day of a month, and sometimes a day of the week and a year. There are several types of calendar watches.
Caliber (Calibre): A term often used to indicate a particular type of mechanism, its shape, layout, size, origin or its maker.
Case: A housing for parts of a watch. It is most usually crafted in stainless steel, although watchmakers use a number of materials to make the central part of a timepiece – titanium, gold, silver, platinum, bronze, ceramic…
Caseback: The opposite side of a case that lies against the wrist. A caseback may be transparent or solid. It is often inscribed with a brand’s logo, a name, important features…
Chronograph: A wrist watch with a stopwatch functions, which counts and shows elapsed time. There are many variations of chronographs. Analog watches use the center seconds hand that shows time on the main dial, or displays elapsed hours, minutes and seconds through sub-dials. Digital timepieces show measured time on the digital screen of the watch face. In conjunction with specialized scales, chronographs can give some other useful information, such as determining speed or distance. Some chronographs measure more than one event at a time.
Chronometer: A high quality watch that has passed rigorous tests in various temperatures and positions, set by the official Swiss testing laboratory called the Controle Officiel Suisse des Chronometeres (COSC). While mechanical movements must be accurate to -4/+6 seconds per day to be officially certified chronometers, quartz movements must be accurate to +/-0.2 seconds per day.
Complication: Other watch functions besides timekeeping. For example, a chronograph, an alarm or an annual calendar are watch complications. Other ‘more complicated’ complications are a minute repeater, a tourbillon, a perpetual calendar, a split second chronograph…
COSC: The official Swiss Chronometer Testing Institute that puts every chronometer watch through the rigorous, 15-day testing procedure to verify the precision of a watch.
Countdown Timer: A feature that shows how much of a pre-set period of time has passed. Some countdown timers send a warning signal a few seconds before time elapses. They are often used by yacht racers, when they must prepare a yacht before the start of a regatta.
Crown: A button on the outside of a case, used for setting the time and the calendar. A crown is also used to wind the mainspring of a mechanical watch. See Screw-Down Crown, Winding Crown
Crystal: A transparent cover on a watch face (sometimes on a caseback) made of glass, synthetic sapphire, mineral or plastic.
Day/Date Watch: A timepiece that displays both, the date and the day of the week.
Day/Night (AM/PM) Indicator: A device that displays whether the indicated time is AM or PM. It is mostly a characteristic of timepieces with a GMT/Dual time indicator or a World Time Display.
Deployment Buckle: A type of a buckle that is extendable. It is easyly put on and removed, it reduces the stress of a band and is more comfortable on the wrist.
Depth Alarm: An alarm on diving timepieces that warns a diver, when the pre-set depth is exceeded.
Dial: A watch face. On quality watches, numerals, indexes, a logo and a surface design are applied separately.
Digital watch: A watch that indicates time through digits. LCD display is often used to show numerals.
Dual Timer: A watch that displays local time as well as time in at least one other time zone. A twin dial, an extra hand, sub-dials, or other complications are commonly used to show dual times. See GMT, World Time Display.
Elapsed Time Rotating Bezel: A graduated rotating bezel that measures periods of time. The bezel can be turned, so that the wearer can align the zero on the bezel with a seconds or a minutes hand and then read elapsed time of the bezel.
Engine Turning: A decorative engraving, usually on the a watch face.
Escapement: A device in a mechanical movement which regulates the rotation of the wheels and, in the finale instance, the movement of hands. The escapement, controlled by the periodic swing of a pendulum or a balance wheel, converts continuous rotational motion into an oscillating or back and forth motion (which produces a “ticking” sound). It allows the gears to advance or “escape” a fixed amount with each swing and to move hands forward at a steady rate. Another function of the escapement is to keep a pendulum or a balance wheel moving by giving it a small push with each swing.
ETA: One of the leading movement manufacturers. Many top-end watch brands use Swiss-made ETA movements in their watches.
Flyback hand: A chronograph complication that instantly restarts timing when the hand is reset to zero.
Gasket: Gaskets seal a case back, a crystal, and a crown to protect a watch from water infiltration.
Gear Train: The system of gears which transmits power from the mainspring to the escapement.
GMT Time Zone: Greenwich Mean Time (GMT) is also known as Zulu Time and UTC (Universal Time Coordinated). The standard by which all World Time is set was agreed at the 1884 International Meridian Conference atWashingtonDC,USA. It placedGreenwich on the Prime Meridian (Zero Longitude). Greenwich Mean Time or GMT is the time standard against which all other time zones in the world are referenced. Generally when the GMT term is used with watches it refers to the ability of a watch that shows local time and the time in at least one other time zone in a 24 hour mode.
Grande Sonnerie: A type of repeater that indicates time by sounds, when a wearer pushes the button.
Guilloche: A French term for the Engine Turning – an engraving technique that forms very artistic repetitive patterns and interesting details.
Hairspring: A very fine part of a mechanical watch that causes the recoil of the balance wheel. The regulator lever of a hairspring adjusts the speed, regulating watch accuracy. It is also known as a balance spring.
Helium Escape Valve: A feature found on some high-end professional diving watches, which provides operations at great depths, for prolonged periods of time. It lets out extra pressure during decompression, by allowing helium to escape.
Horology: The science of time measurement, watch design and constructing.
Index: An hour indicator on an analog watch dial, used instead of numerals.
Jewels: Synthetic sapphires or rubies that act as bearings for gear trains in a mechanical watch, reducing friction.
Lap Timer: A chronograph function that provides timing race segments. At the end of a lap, a timer is stopped and returned to zero to start timing the next lap. Thanks to the Lap Memory, wearers can overview lap times on a digital display.
Liquid-Crystal Display (LCD): A digital watch display that shows time electronically by means of a liquid held in a thin layer between two transparent plates.
Luminous: A coating on watch hands and markers, which “glow in the dark”, allowing readability in low-light conditions.
Lugs: Arms of the case to which the band/bracelet is attached.
Main Plate: A base plate on which all other parts of a watch movement are mounted.
Mainspring: The power source in mechanical watches. The mainspring uses stored energy to turn the clock’s wheels as it unwinds.
Manual Wind Movement: A mechanical movement that operates by winding a crown manually, which winds the mainspring in the barrel that powers a timepiece. Fully wounded, it will beat for the specified amount of time (generally 35-45 hours). See Automatic Winding Movement, Quartz Movement, Winding Crown.
Measurement Conversion: A feature, usually consists of a graduated scale on the bezel, which allows a wearer to convert one type of measurement into another (miles into kilometers, pounds into kilograms…).
Mechanical Movement: A movement that beats without an outside energy source. A mechanism is constructed of multiple parts, gears, screws and springs. By winding the mainspring (either by manual winding or via automatic winding), a mechanical movement starts working, moving a watch hand and providing the accurate time.
Minute Repeater: A special type of watch that indicates hours, quarters and minutes both visually and by sound. The repeater is activated by the button on the case edge. This is a very complicated feature that makes a watch highly expensive.
Moon-phase: An indicator for the phases of the moon through 29 1/2 days.
Mother-of-Pearl: An iridescent milky interior of the freshwater mollusk that is sliced thin and used as a decoration on watch dials. Mother-of-pearl comes in milky white, silvery gray, yellow, gray blue, pink and salmon.
Pedometer: A device that counts the number of strides taken by the wearer by responding to the impact of the wearer’s steps.
Perpetual Calendar: A calendar that is programmed to show the date, day, month & leap year cycle at the minimum (some display the year and Moon phase). They are adjusted for even and odd months and for the leap year, until the year 2100.
Power Reserve: The amount of energy, stored up to keep a timepiece working until it runs down.
Power Reserve Indicator: An indicator that shows a number of hours that a watch will run before it requires to be wound again.
Pulsimeter: A chronograph scale that measures a pulse rate.
Push-piece: A button that is pressed to activate watch functions (a chronograph, alarms, a date corrector etc.).
Quartz Crystal: A tiny piece of synthetic quartz that oscillates at the rate of 32.768 times a second, dividing time into equal segments.
Quartz Movement: An electronic watch movement, with a quartz crystal that oscillates when a battery is applied to it. Vibrations of a tiny crystal provide precise timing. New quartz technology enables a movement to be recharged without a battery replacement. The power is provided either by body motion, light or body heat.
Retrograde watch: A timepiece with a retrograde display that shows functions in a linear way, rather than in a usual manner, with hands going round in a circle.
Rotating Bezel: A ring surrounding the watch face that can be turned. Different types of rotating bezels feature various timekeeping and mathematical functions.
Rotor: A key part of a self-winding mechanism, which automatically winds the mainspring.
Sapphire Crystal: A very hard transparent material commonly used for “scratch-proof” watch glasses.
Screw-Down Crown: A crown that can be screwed into the protective part of a case to insure safely handling under water.
Second Time-Zone Indicator: A dial that allows a wearer to keep track of time in two time zones simultaneously.
Shock Absorber: A resilient bearing which takes up the shocks received by the balance staff and protects its pivots from damage.
Shock Resistance: An ability of a watch to resist a collision that is equal to a shock caused by a knock on a wood floor, after being thrown from the height of 3 feet.
Skeleton Case: A case with a transparent front or back, which allows a clear view on a watch movement.
Slide Rule: A device, consisting of a scale on a dial’s outer rim, which provides mathematical calculations (fuel consumption, climbing times & converting miles into nautical miles or kilometers).
Solar Powered Batteries: Batteries in a quartz timepiece, recharged via solar panels on an interface.
Split Seconds Hand: Two central seconds hands – a flyback hand and a regular chronograph hand move together, with an ability to be stopped independently, so that a wearer can track lap times or different finishing times.
Stopwatch – Chronograph
Stepping Motor: The part of a quartz movement that moves the gear train, which in turn moves watch hands.
Sub-dial: A small dial on the watch that serves either as a chronograph (minute, hour or second counter), a date display or a power-reserve indicator.
Swiss Made: A timepiece is labeled as a Swiss-made only if its movement was assembled, started, adjusted and controlled by the manufacturer in Switzerland. At least 50 percent of movement’s parts need to be produced in Switzerland. A case and a band can be crafted outside of Switzerland, but the components must be completely assembled in Switzerland.
Swiss A.O.S.C. (Certificate of Orgin): A label of a timepiece, which shows that it was assembled in Switzerland, with Swiss made components.
Tachymeter: A common chronograph feature, most often engraved on a bezel, which measures speed according to a predefined distance. Speed can be read in units per hour on the tachometer scale.
Timer: An instrument used for registering intervals of time, without any indication of the time of a day.
Tonneau Watch: A watch shaped like a barrel, with two convex sides.
Totalizer: A mechanism that counts and shows elapsed time, usually on a sub-dial.
Tourbillon: A hi-end addition to a mechanical watch, which eliminates the effects of gravity during the rotation, by mounting the escapement and a balance wheel in a rotating cage. It rotates permanently at the rate of once per minute. A mechanism with a tourbillon complication is usually exposed through a transparent dial.
Uni-directional Rotating Bezel: A rotating bezel that turns only in a counterclockwise direction. It is constructed to prevent rotating by accident, which is especially useful for divers who need to track elapsed time with extreme precision.
Vibration Per Hour: Movement of a pendulum or other oscillating mass, limited by two extreme positions.
Water-Resistance: A characteristic of a watch that can resist a certain level of water-pressure.
Winding: An operation of tightening the mainspring of a mechanism. A watch can be wind by hand (manually, by turning a crown) or automatically (via a rotor which is powered by the movements of a wrist).
World Time Dial: A dial that displays time up to 24 time zones around the world. The time zones are selected by the names of cities, printed on a bezel or on a dial.
Yacht Timer: A Countdown Timer