A – C
Alarm
A function on a watch that will make a sound or vibration at a preset time.
Altimeter
An altimeter measures altitude, or height above sea level. Recording ascent and descent, an altimeter watch is an important piece of equipment for climbers, walkers, mountaineers and, of course, aviators.
Analog/Digital (Duo) Display aka Anadigi
A watch that displays the time, both by hour and minute hands, (an analog display) and by digital digits (a digital display). This is also known as duo display or an AnaDigi watch.
Annual Calendar
A complication showing the date; day and month at the minimum. Many will also display Moonphase. This watch will correctly adjust for short and long months; however, it will not correctly account for leap year - when, once in 4 years, an additional day is added to February making it a 29 day month.
Aperture
A small opening/window found on the dials of some watches in which certain indications are given, such as the hour and the date.
Auto Repeat Countdown Timer
A countdown timer that resets itself as soon as the preset time has elapsed and starts again. The countdown is repeated continuously until the stop button is pushed.
Automatic Winding Movement
Works like a manual-wind mechanical watch, with the addition of a weighted rotor that spins as you move and winds the mainspring for you. Worn daily it stays wound; left unworn it will stop after its power reserve (usually 35–45 hours) and should be given 30–40 turns of the crown before wearing again.
Balance Spring
A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulates the timekeeping. This is also known as a hairspring.
Balance Wheel
The part of a mechanical watch movement that oscillates, dividing time into equal segments. This is the regulating mechanism that controls the watch's timekeeping accuracy.
Barrel
A drum that holds the Mainspring in a mechanical watch. The size of the barrel directly affects the length of the Power Reserve. Some watches feature a Double-Barrel which allows for extra long power reserve. The toothed rim of the barrel drives the train.
Bezel
The ring around the crystal on top of the case. Rotating bezels (one- or two-way) measure elapsed time by aligning their 12 o’clock mark with the start of an event; fixed bezels usually carry a scale such as a tachymeter.
Bi-Directional Rotating Bezel
A bezel that can be moved both clockwise and counter-clockwise. It is used for keeping track of elapsed time. Allowing the bezel to be rotated either way gives maximum flexibility to beginning the timing.
Bracelet
The metal strap that goes around the wearer's wrist. A watch bracelet is typically made up of flexible, separate links that can be added or removed to adjust the bracelet's length.
Breguet Spring
The spiral hairspring on which the balance swings tends to bunch on opposite sides as it expands or contracts. The constant shift in their gravity disturbs the rate of balance, and Breguet solved the problem in 1795 by upraising the last coil of the spring and giving it a smaller curve. This Breguet overcoil encouraged the spring to develop concentrically, improving the rate of the watch and reducing the wear on the balance pivots.
Bridge
A part that is fixed to the main plate to form the frame of a watch movement. All other parts are mounted inside the frame.
Calendar
A function that indicates day of the month, and sometimes day of the week and the year.
Caliber or Calibre
Since the early 18th Century, the calibre of a movement has denoted the position and size of its different components, notably the wheel train and the barrel. Today the term is generally used to refer to the movement, its origins or its maker.
Cambered
This refers to a domed or arched crystal.
Case
The metal housing that contains a watch's parts. Stainless steel is most commonly used. While titanium, platinum, gold and silver are also common, they will increase the price of the watch.
Chronograph
A watch with a stopwatch function. A Chronograph both measures and displays elapsed times in addition to showing conventional time. Generally, the chronograph mechanism is driven by the movement of the watch and operated by two buttons on the edge of the case which start, stop and reset the chronograph. Usually the chronograph seconds hand is the large centre seconds with sub-dials for elapsed minutes and hours - although the exact display may vary.
Chronometer
A precision watch whose movement has been tested and certified by the Swiss COSC laboratory: measured at three temperatures and in five positions over 15 days, and accurate to -4/+6 seconds a day for mechanical movements (±0.2 seconds for the few certified quartz movements).
Complication
A watch with functions other than timekeeping. A simple complication would include various chronographs, alarm, annual calendar and GMT functions, to mention a few. A watch with high complications would be called a Grand Complication and would include a perpetual calendar, Tourbillon, minute repeater or equation of time functions, and others. A watch with any additional function is called a complicated watch.
COSC
The official chronometer testing organization in Switzerland COSC "Controle Officiel Suisse des Chronometres".
Countdown Timer
This allows the wearer to know how much of a preset time has passed. Some Quartz versions sound a warning a few seconds before the pre-set time has elapsed.
Crown
The grooved knob on the outside of the case, used for setting the hands on a watch, and the day and date, where applicable. It is also used for winding the mainspring of a mechanical watch. The crown is also known as a winder or winding stem.
Crystal
This is the clear cover on the watch face (dial). It may be made of glass, plastic, mineral crystal or sapphire crystal (a scratch-resistant synthetic material). Its purpose is to protect the watch face.