Adjustment (or Regulation) – A feature that ensures the movement’s time is accurate by regulating its beats. The time may not run consistently when there’s a temperature or position change, but the regulation feature speeds the beats up or slows them down when necessary.
Altimeter – A device that determines the height above sea level, also known as altitude, by responding to changes in barometric pressure.
Amplitude – Measures, in terms of degrees, the maximum angle in which a balance swings from its position of rest. The amplitude can change depending on the position of the watch, but if the amplitude is too high or too low, then it may indicate a problem with the watch’s movement.
Analog (Display and Watch) – An analog watch uses hands and a dial to show the time.
Annual Calendar – A calendar that automatically adjusts for the months’ varying lengths, but unlike perpetual calendars, annual calendars need to be reset every year.
Anti-magnetic – The watch is not affected by magnetic fields. If the watch does become magnetized, it will often not keep accurate time, generally running slow.
Aperture – A small opening in the dial used to display information such as date, day, month, or moon-phase.
Assembling – The process of putting together the components of a watch. Although this process used to be done by hand, it is largely done by machine. However, the inspection and testing is still done by hand.
Automatic Movement – A mechanical movement that is wound by everyday movements of the wearer. If an automatic watch isn’t worn for a few days, it will need to be wound to get started again.
Balance – Necessary for a mechanical watch, the balance is a wheel that rotates back and forth on an axle. The balance spring, also known as a hairspring, is a very fine spring that returns the balance wheel back to its neutral position. Then the balance wheel oscillates and divides time into equal portions. Without a well-constructed balance, the watch will not be precise.
Balance Spring (or Hairspring) – The balance spring, also known as a hairspring, is a very fine spring that returns the balance wheel back to its neutral position. The spring’s elasticity ensures that the balance swings back and forth at a regular rate.
Barrel – A thin cylindrical box that holds the mainspring of a watch.
Bezel – The ring that surrounds the watch face and secures the glass or crystal covering the dial. Depending on the watch, the bezel can rotate to measure elapsed time or to indicate the time in a second time zone.
Bracelet – A bracelet is a type of watch band that often resembles links; a bracelet can be ceramic or metal.
Bridge – A flat, typically narrow metal plate that holds the rotating watch gears. Jewels may be fit into the bridge to hold rotating pivots of a moving part or parts.
Cabochon – A smooth gemstone which has been carved into a round shape. Cabochons are used mainly for decoration.
Calendar – A feature that shows the day of the month. Some watches will even show the day of the week and the year.
Caliber – Numbers or letters that are used to denote a particular watch movement. For example, Caliber 3135 describes Rolex’s self-winding mechanical movement.
Case – The metal housing of a watch’s internal parts or movements. The case can come in many different shapes, and it can be made out of a variety of materials such as stainless steel, gold, silver, titanium, platinum, and brass.
Caseback – The underside of a watch case that lies against the skin. Some casebacks are made transparent with a crystal cover which allows you to view the inner workings of the watch.
Chronograph – A device that measures elapsed time, also known as a stopwatch. A typical chronograph has two pushers on the side of its case; the top pusher starts and stops the timer and the bottom pusher resets the timer to zero.
Chronometer – For a watch to be considered a chronometer, it needs to have passed a series of tests by a certification agency such as the Controle Officiel Suisse des Chronometres, or C.O.S.C. In order to pass the test, the watch is tested in various temperatures and positions.
Complication – A device or feature in a watch movement that has a purpose other than timekeeping. Some common complications include alarms, calendars, chronographs, repeaters, and tourbillions.
COSC (or C.O.S.C) – This is an abbreviation for Controle Officiel Suisse des Chronometres, or Swiss Chronometer Testing Bureau. This agency tests watches to verify the watch’s precision. If the watch meets their standards, then it is issued a chronometer certificate.
Countdown Timer – A function that allows the wearer to keep track of how much time has elapsed in a predefined period.
Crown – A knob or button on the outside of the case that is used to wind and set a watch’s time and calendar.
Crystal – A transparent cover that protects the watch dial. The crystal can be made of glass crystal, synthetic sapphire, or plastic.
Day/Date Watch – A watch that indicates both the date and the day of the week.
Day/Night Indicator – A colored or shaded band on a world time watch that indicates which times zones are in daylight and which are in darkness.
Deployment Buckle – In contrast to the tang buckle, a deployment buckle uses hinged extenders to pop open and fasten. Deployment buckles are easier to put on than the standard belt buckle-like closure.
Dial – The face of a watch. Some watches have additional features on the watch face such as the date, a chronograph, or day/night indicators; these dials are called subsidiary dials or subdials.
Digital – In contrast to analog watches, digital watches use a numerical display to show the time.
Dual Time Zone – A watch that indicates the local time as well as at least one other time zone.
Ebache – An unassembled watch movement that will be assembled into a complete watch at a later date. Many times the movements, dials, hands, and cases are manufactured by separate makers and then later assembled.
Elapsed Time Rotating Bezel – The rotating bezel can be used to keep track of periods of time. The bezel, which includes minute markers, can be turned to align the zero on the bezel with the watch’s second or minute hand. For example, after 5 minutes have elapsed, the minute hand will point to the “5†marker on the bezel.
Engine Turning – A decorative engraving, usually appearing on the watch face.
Escapement – A device in a mechanical movement that controls the rotation of the wheels, thereby controlling the motion of the hands.
Flyback Chronograph – A chronograph in which the seconds hand can be stopped, returned to zero, and restarted instantly by pushing only one button. Typical chronographs need to be stopped, returned to zero, and started with three separate steps. The flyback function is useful for timing events that occur in rapid sequence, such as the laps in a race.
Gasket – Used in water resistant watches to seal the caseback, the crystal, and the crown from water infiltration. Gaskets should be checked every few years to maintain water resistance.
Gear Train – The system of gears which transmits power from the mainspring to the escapement.
Geneva Seal (Poinçon de Genève) – An independent bureau in Geneva awards the Geneva Seal to watches that have passed its inspection. First and foremost, the submitted watch needs to be mechanical and the movement needs to be assembled, adjusted, and cased-up in the Canton of Geneva. If a watch meets this initial criteria, then it undergoes extensive testing. Previously the Geneva Seal focused mainly on the movement’s finishing and material. However, in 2011 the list of requirements was updated to include accuracy, power reserve, water resistance, and functionality.
Geneva Waves – Also called Geneva stripes, the Geneva waves are decorative wave-like designs found on the plates, bridges, cocks, or rotors of many watches.
GMT (Greenwich Mean Time) – This is the time at the Royal Observatory in Greenwich, England, which is located at the prime meridian. GMT is used to determine the time all over the world. GMT watches allow the wearer to track Greenwich mean time in addition to their local time zone; however, the wearer can choose to track any two time zones of their choosing.
Gold Plating – A layer of gold that is electro-deposited onto a metal.
Going Train (or Wheel Train) – See below, Wheel Train.
Grande Sonnerie – A type of repeater that sounds the hours and quarter hours when the wearer presses a lever or button.
Guilloché – A decorative pattern that is popular on watch dials and plates. This pattern is achieved by using an intricate engraving machine.
Hairspring (or Balance Spring) – See above, Balance Spring.
Hallmark – A mark stamped on the watch case to provide information about the metal used, the watch’s origin, the year of manufacture, and the name of the case’s maker. Some hallmarks will also show the trademark of the watch company, a reference number, and a serial number.
Hand-Wound Movement (or Manual-Wind Movement) – See below, Manual-Wind Movement.
Horology – The art or science of making timepieces or of measuring time.
Incabloc – A shock absorber system that protects a watch’s balance from breaking if dropped.
Jewels – Synthetic rubies or sapphires that reduce friction by acting as bearings for gears in a mechanical watch.
Jump Hour Indicator – Replacing the hour hand, the jump hour indicator typically shows the hours by means of a numeric window.
LCD (Liquid-Crystal Display) – A digital watch that shows the time electronically by holding the liquid in a thin layer between two transparent plates. This type of display is used in nearly all digital quartz watches.
Lugs – Also known as horns, lugs are projections on the watch case that connect the bracelet or strap to the watch.
Mainspring – Found in the barrel, the mainspring is the driving force that runs the watch.
Manual-Wind Movement (or Hand-Wound Movement) – In contrast to an automatic movement, a manual-wind movement must be wound by the wearer in order to run. Oftentimes wearers will need to wind the watch daily; however, some watches can go for up to eight days without needing to be wound. You wind the movement by turning the crown.
Mechanical Watch – Contrary to quartz watches, these mechanical watches include intricate movements that are powered by a mainspring and regulated by a balance.
Micron – Unit of measurement of the thickness of the gold-plating. 1 micron equals 1/1000 mm.
Moon-Phase Display – A window on a watch face that shows the current phase of the moon.
Movement – The complete inner mechanism of a watch. The movement keeps time, moves the watch hands, regulates the calendar, etc.
Perlage – A decorative design that consists of small, overlapping circles often found on the watch’s plates and bridges.
Perpetual Calendar – A calendar that automatically adjusts for the months’ varying lengths, and unlike annual calendars, the perpetual calendar accounts for leap year. These calendars are programmed to be accurate until the year 2100.
Power Reserve – The length of time that a mechanical movement can run before needing to be rewound. A typical mechanical watch can run for 36 to 48 hours before needing to be wound, but some watches can run for a week or longer.
Power-Reserve Indicator – A feature of a mechanical watch that shows the length of time a watch can run before needing to be wound.
Quartz Watch – A movement that allows the watch to keep time without being wound. Some quartz watches require a battery that needs to be replaced every 1.5 years, but newer watches can be recharged without battery replacement. There are three different ways to recharge a quartz watch: through a solar cell, through body heat, or through body motion.
Rattrapante (or Splits Seconds Chronograph) – Unlike a standard chronograph, this type of chronograph has two seconds hands, so the wearer can stop one hand while the other hand continues to run. The rattrapante hand is started simultaneously with the main chronograph hand. However, the rattrapante hand can be stopped independently, multiple times. Then the rattrapante hand is “catches up†with main chronograph hand. This type of chronograph is useful if the wearer wants to time simultaneous events such as two runners competing in a race. The watch can also time the laps of a single runner in a race.
Regulation (or Adjustment) – See above, Adjustment.
Repeater – A device that chimes the time when a slide or button on the watch case is pushed. Some repeaters are able to chime the time to the latest minute, but other repeaters chime the time to the latest quarter hours or 5 minutes.
Retrograde Display – A display in which the hand moves over a graduated arc, instead of the full circle, to indicate the time or date. When the hand reaches the end of the arc, it instantly returns to its starting position.
Rotating Bezel – A bezel is the ring that surrounds the watch face, and a rotating bezel can be turned. This feature can be used for multiple different timekeeping and mathematical functions. For example, a rotating bezel could be used to track the time in a second time zone.
Rotor – In an automatic watch, the rotor is a weight that swings back and forth when the wearer moves his/her arm. It is this swinging weight that winds the movement’s main spring. However, this means that the rotor only winds the mainspring when the watch is worn.
Sapphire Crystal – Sapphire crystals are synthetic sapphires that are transparent, shatter-resistant, and scratch-resistant. Sapphire crystals can be used as the protective cover over the watch face.
Screw-Down Crown – A crown is used to wind and set a watch’s time and calendar. A screw-down crown is a type of crown that can be tightly screwed to the watch case. This type of crown is typically used in water-resistant watches.
Shock Protection – When a watch experiences a strong blow, a small spring protects the balance from taking on damage.
Shock Resistance – A shock-resistant watch, as defined by U.S. government regulation, should withstand an impact equal to being dropped onto a wood floor from a height of three feet.
Skeleton Case – A type of watch that has a transparent front or back which allows the wearer to view the inner workings of the watch movement.
Slide Rule – A rotating bezel that allows the wearer to perform complicated mathematical calculations, such as multiplication, division, and conversions.
Split Seconds Chronograph (or Rattrapante) – See above, Rattrapante
Strap – A strap is a type of watch band that is often made out of leather, nylon, or rubber.
Subsidiary Dial – A small dial on the watch face that shows additional information, such as the date, alarms, dual time zones, calendars, or elapsed time on a chronograph.
Sweep Seconds-Hand – A second hand that is mounted in the center of a dial, instead of a subsidiary dial.
Swiss Made – In order for a watch to be considered Swiss Made, it must meet the following requirements. (1) The watch has a Swiss movement, meaning that at least 50% of the movement was made in Switzerland. (2) Both the watch and the movement are assembled and inspected in Switzerland.
Tachymeter (Tachometer) – A numerical scale on the dial or bezel of a chronograph that is used to measure speed over a pre-measured distance.
Tank Watch – A rectangular watch designed by Louis Cartier in 1917. The shape of the watch was inspired by World War I military tanks.
Tonneau Watch – A watch shaped like a barrel, with two convex sides.
Tourbillon – A device in mechanical watches that eliminates time keeping errors caused by gravity. The tourbillon consists of a cage that holds the escapement and the balance, and it rotates continuously at the rate of once per minute. The constant rotation eliminates the effects of gravity caused when the watch is in a vertical position.
Triple Date – A watch with a triple date calendar shows the day, date, and month.
Tritium – An isotope of hydrogen that is used to make the watch hands and hour markers glow in the dark.
Uni-Directional Rotating Bezel – A rotating bezel, typically found on divers’ watches, which can only rotate counter-clockwise. If a diver is timing her/her remaining air supply and knocks the bezel by mistake, it can only move in the direction that would err on the side of safety, preventing the diver from overestimating his/her remaining air supply.
Water-Resistant – A watch that can withstand light moisture or water splashes. If a watch can be submerged in water, then it must indicate the depth at which it maintains water resistance. Note: There’s no such thing as a 100% water-proof watch.
Wheel Train (or “Going Trainâ€) – The series of wheels and pinions that transmit power from the mainspring to the escapement. This process also powers the minute and second hands.
Winding – The action of tightening the watch’s mainspring. This can be done by hand (by means of turning the crown) or automatically (by means of the rotor).
Winding Stem – The stem connects the interior and exterior of the watch. On one end of the stem is the crown, and wearer turns or pushes the crown to wind and set the mechanical movement.
World Time Watch – These watches can display, most often on the watch dial, the current time in up to 24 time zones around the world.