(Sort in alphabetical order)

A-Z Index : Numbers

12-hour (24-hour) recorder (or register):
A sub-dial on a chronograph (see chronograph) that can time periods of up to 12 or 24 hours.

24-hour movement:
A special movement wehere the hour hand goes around the dial only once a day. This is also called 'Real Military Time'.

30-minute recorder (or register):
A sub-dial on a chronograph (see "chronograph") that can time periods of up to 30 minutes.

A-Z Index : A

alarm:
The watch alerts you with beeps at pre-set time(s).

analog:
A watch that shows the time using hour and minute hands.

analog - digital display:
A watch that shows the time by means of hour and minute hands (analog display) as well as by numbers (a digital display).

aperture:
Small opening. The dials of some watches (in French: montres à guichet) have apertures in which certain indications are given (e.g. the date, the hour, etc).

applique:
Applique or applied chapters are numerals or symbols cut out of a sheet metal and stuck or riveted to a dial.

assembling:
Process of fitting together the components of a movement. This was formerly done entirely by hand, but the operations have now been largely automated. Nevertheless, the human element is still primordial, especially for inspection and testing.

assortiment:
French term for the parts used for making an escapement.

automatic watch:
A watch whose mainspring is wound by the movements or accelerations of the wearer's arm. On the basis of the principle of terrestrial attraction, a rotor turns and transmits its energy to the spring by means of an appropriate mechanism. The system was invented in Switzerland by Abraham-Louis Perrelet in the 18th century.

automatic winding (or self-winding):
This term refers to a watch with a mechanical movement (as opposed to a quartz or electrical movement). The watch is wound by the motion of the wearer's arm rather than through turning the winding stem. A rotor that turns in response to motion winds the watch's mainspring. If an automatic watch is not worn for a day or two, it will wind down and need to be wound by hand to get it started again.

A-Z Index : B

balance:
Moving part, usually circular, oscillating about its axis of rotation. The hairspring coupled to it makes it swing to and fro, dividing time into exactly equal parts. Each of the to-and-fro movements of the balance ("tick-tack") is called an "oscillation". One oscillation is composed of two vibrations.

battery reserve indicator (or end of battery indicator):
Some battery-operated watches have a feature that indicates when the battery is approaching the end of its life. This is often indicated by the second hand moving in two second intervals instead of each second.

barrel:
Thin cylindrical box containing the mainspring of a watch. The toothed rim of the barrel drives the train.

bezel:
The ring that surrounds the watch dial (or face). The bezel is usually made of gold, gold plate or stainless steel.

bi-directional rotating bezel:
A bezel that can be rotated either clockwise or counterclockwise. These are used for mathematical calculations such as average speed or distance (see "slide rule") or for keeping track of elapsed time(see "elapsed time rotating bezel").

bridge:
Complementary part fixed to the main plate to form the frame of a watch movement. The other parts are mounted inside the frame.

built-in illumination:
Lighting on a watch dial that allows the wearer to read the time in the dark.

A-Z Index : C

calendar:
A feature that shows the date, and often the day of the week. There are several types of calendar watches. Most calendar watches show the information digitally through an aperture on the watch face. Some chronograph watches show the information on sub-dials on the watch face.

(Watch-) case:
Container that protects the watch-movement from dust, damp and shocks. It also gives the watch as attractive an appearance as possible, subject to fashion and the taste of the public.

chronograph:
Watch or other apparatus with two independent time systems: one indicates the time of day, and the other measures (stopwatch function) brief intervals of time. Counters registering seconds, minutes and even hours can be started and stopped as desired. It is therefore possible to measure the exact duration of an event. There are many variations on the chronograph. Some operate with a center seconds hand which keeps time on the watch's main dial. Others use sub-dials to time elapsed hours, minutes and seconds. Still others show elapsed time on a digital display on the watch face. Some chronographs can be used as a lap timer (see "flyback hand" and "split seconds hand"). The accuracy of the stopwatch function will commonly vary from 1/5th second to 1/100th second depending on the chronograph. Some chronographs will measure elapsed time up to 24 hours. Watches that include the chronograph function are themselves called "chronographs." When a chronograph is used in conjunction with specialized scales on the watch face it can perform many different functions, such as determining speed or distance (see "tachometer"). Do not confuse the term "chronograph" with "chronometer." The latter refers to a timepiece, which may or may not have a chronograph function, that has met certain high standards of accuracy set by an official watch institute in Switzerland.

chronometer:
Technically speaking, all watches are chronometers. But for a Swiss made watch to be called a chronometer, it must meet certain very high standards set by the Swiss Official Chronometer Control (C.O.S.C.). If you have a Swiss watch labeled as a chronometer, you can be certain that it has a mechanical movement of the very highest quality -- undergone a series of precision tests in an official institute. The requirements are very severe: a few seconds per day in the most unfavourable temperature conditions (for mechanical watches) and positions that are ordinarily encountered.

countdown timer:
A function that lets the wearer keep track of how much of a pre-set period of time has elapsed. Some countdown timers sound a warning signal a few seconds before the time runs out. These are useful in events such all kinds of race.

crown:
Also called a stem or pin, a crown is the knob/button on the outside of the watch case that is used to set the time and date. In a mechanical watch the crown also winds the mainspring. In this case it is also called a "winding stem". A screw in (or screw down) crown is used to make a watch more water resistant. The crown actually screws into the case, dramatically increasing the water-tightness of the watch.

crystal:
The transparent cover on a watch face made of glass crystal, synthetic sapphire or plastic. Better watches often have a sapphire crystal which is highly resistant to scratching or shattering.

A-Z Index : D

depth alarm:
An alarm on a divers' watch that sounds when the wearer exceeds a pre-set depth.

depth sensor/depth meter:
A device on a divers' watch that determines the wearer's depth by measuring water pressure. It shows the depth either by analog hands and a scale on the watch face or through a digital display.

dial:
The watch face (plate of metal or other material). Dials vary verymuch in shape, decoration, material, etc. The indications are given by means of numerals, divisions or symbols of various types.

digital watch:
A watch that shows the time through digits rather than through a dial and hands (analog) display.

direct-drive:
Refers to a seconds-hand that moves forwards in little jerks.

display:
Indication of time or other data, either by means of hands moving over a dial (analogue display) or by means of numerals appearing in one or more windows (digital or numerical display); these numerals may be completed by alphabetical indications (alphanumerical display) or by signs of any other kind. Example: 12.05 MO 12.3 = 12 hours, 5 minutes, Monday 12th March. Such displays can be obtained by mechanicalor electronic means.

diving watch:
A watch that is water resistant to 200M. Has a one way rotating bezel and a screw-on crown and back. Has a metal or rubber strap (not leather). Has a sapphire crystal and possibly, a wet-suit extension.

A-Z Index : E

elapsed time rotating bezel:
A graduated rotating bezel (see "rotating bezel") used to keep track of elapsed time. The bezel can be turned so the wearer can align the zero on the bezel with the watch's seconds or minutes hand. After a period of time passes, you can read the elapsed time off the bezel. This saves you having to perform the subtraction that would be necessary if you used the watch's regular dial.

escapement:
Device in a mechanical movement that controls the rotation of the wheels and thus the motion of the hands. Set of parts (escape wheel, lever, roller) which converts the rotary motion of the train into to-and-fro motion (the balance).

A-Z Index : F

factory (works):
In the Swiss watch industry, the term manufacture is used of a factory in which watches are manufactured almost completely, as distinct from an "atelier de terminage", which is concerned only with assembling, timing, fitting the hands and casing.

flyback hand:
A seconds hand on a chronograph that can be used to time laps or to determine finishing times for several competitors in a race. Start the chronograph, putting both the flyback hand and the regular chronograph seconds hand in motion. To record a lap time or finishing time, stop the flyback hand. After recording the time, push a button and the hand will "fly back" to catch up with the constantly moving elapsed-time hand. Repeat the process to record as many lap times or finishing times as needed. In chronographs with numerical display, a "function" having the same effect.

A-Z Index : G

gear train:
The system of gears which transmits power from the mainspring to the escapement.

glass (Crystal):
Thin plate of glass or transparent synthetic material, for protecting the dials of watches, clocks, etc.

gold plated:
A layer of gold electroplated to a base metal.

A-Z Index : H

hand:
Indicator, usually made of a thin, light piece of metal, very variable in form, which moves over a graduated dial or scale. Watches usually have three hands showing the hours, minutes and seconds.

A-Z Index : I

integrated bracelet:
A watch bracelet that is incorporated into the design of the case.

A-Z Index : J

jewels:
Synthetic sapphires or rubies that act as bearings for gears in a mechanical watch. The jewels reduce friction to make the watch more accurate and longer lasting. Generally made of synthetic material, except for the precious or semi-precious stones (ruby, sapphire, garnet) which are sometimes used in "de luxe" watches.

A-Z Index : K

kinetic:
Refers to the Seiko line of Kinetic watches. This innovative technology has a quartz movement that does not use a battery. Movement of your wrist charges a very efficient capacitor which powers the quartz movement. Once the capacitor is fully charged, mens models will store energy for 7-14 days without being worn. Ladies models store energy for 3-7 days. Of course, if the watch is worn every day the capacitor is continually recharged. The watch alerts you to a low capacitor charge when the seconds hand starts to move in two second intervals.

A-Z Index : L

lap timer:
A chronograph function that lets the wearer time segments of a race. At the end of a lap, he stops the timer, which then returns to zero to begin timing the next lap.

liquid-crystal display (LCD):
A digital watch display that shows the time electronically by means of a liquid held in a thin layer between two transparent plates. All LCD watches have quartz movements.

lugs:
Projections on a watch face to which the watch band or bracelet is attached.

Luminescence - Luminous:
Watch (dial, hands) that glows in the dark. Photoluminescent paints that absorbed energy from external light sources in the UV spectrum and reemitted it over a period of time. Today there are 3 main materials for creating Luminescence: LumiNova (zinc sulfide-based), Super-LumiNova (up to 10 times brighter than LumiNova) and Tritium gas tubes (GTLS). It's worth noting that GTLS is banned in certain countries.
Comparison between Super-LumiNova and GTLS.

A-Z Index : M

main plate:
Base plate on which all the other parts of a watch movement are mounted.

mainspring:
The driving spring of a watch or clock, contained in the barrel.

marine chronometer:
Highly accurate mechanical or electronic timekeeper enclosed in a box (hence the term box chronometer), used for determining the longitude on board ship. Marine chronometers with mechanical movements are mounted on gimbals so that they remain in the horizontal position is necessary for their precision.

measurement conversion:
A feature, usually consisting of a graduated scale on the watch's bezel, that lets the wearer translate one type of measurement into another-miles into kilometers, for instance, or pounds into kilograms.

mechanical movement:
A movement powered by a mainspring, working in conjunction with a balance wheel. Most watches today have electronically controlled quartz movements and are powered by a battery. However, mechanical watches are currently enjoying a resurgence in popularity.

movement:
The inner mechanism of a watch that keeps time and moves the watch's hands, calendar, etc. Movements are either mechanical or quartz.

A-Z Index : P

power reserve indicator:
A feature that shows when the watch will soon need a new battery or winding. A battery reserve indicator on a quartz watch informs the wearer when the battery is low. Often this is indicated by the seconds hand moving at two or three-second intervals. Seiko's Kinetic watches are quartz watches that do not have a battery (see Kinetic). When a Seiko Kinetic needs to be wound, the seconds hand will also move in two second intervals.

A-Z Index : Q

quartz movement:
A movement powered by a quartz crystal to. Quartz crystals are very accurate. They can be mass produced which makes them less expensive than most mechanical movements which require a higher degree craftsmanship.

A-Z Index : R

rotating bezel:
A bezel (the ring surrounding the watch face) that can be turned. Different types of rotating bezels perform different timekeeping and mathematical functions.

rotor:
The part of an automatic (or self-winding) mechanical watch that winds the movement's mainspring. It is a flat piece of metal, usually shaped like a semicircle, that swivels on a pivot with the motion of the wearer's arm.

A-Z Index : S

sapphire crystal:
A crystal made of synthetic sapphire, a transparent, shatter-resistant, scratch-resistant substance.

screw-lock crown:
A crown that can be screwed into the case to make the watch watertight. The time can be set by unscrewing counter-clockwise and pulling out the crown as instruction book indicates; following the adjustment, push and screw clockwise to tighten securely.

See-through skeleton back:
Case back made of transparent material such as hardened mineral crystal which enables the main parts of the watch to be viewed while working.

second:
Basic unit of time (abbr. s or sec), corresponding to one 86,000th part of the mean solar day, i.e. the duration of rotation, about its own axis, of an ideal Earth describing a circle round the Sun in one year, at a constant speed and in the plane of the Equator. After the Second World War, atomic clocks became so accurate that they could demonstrate the infinitesimal irregularities (a few hundreths of a second per year) of the Earth's rotation about its own axis. It was then decided to redefine the reference standard; this was done by the 13th General Conference on Weights and Measures in 1967, in the following terms: "The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the fundamental state of the atom of caesium 133". Conventionally, the second is subdivised into tenths, hundredths, thousendths (milliseconds), millionths (microseconds), thousand-millionths (nanoseconds) and billionths (picoseconds).

second time-zone indicator:
An additional dial that can be set to the time in another time zone. It lets the wearer keep track of local time and the time in another country simultaneously.

shock resistance:
As defined by U.S. government regulation, a watch's ability to withstand an impact equal to that of being dropped onto a wood floor from a height of 3 feet.

skeleton:
Skeleton watch: watch in which the case and various parts of the movement are of transparent material, enabling the main parts of the watch to be seen.

slide rule:
A device, consisting of logarithmic or other scales on the outer edge of the watch face, that can be used to do mathematical calculations. One of the scales is marked on a rotating bezel, which can be slid against the stationary scale to make the calculations. Some watches have slide rules that allow specific calculations, such as for fuel consumption by an airplane or fuel weight.

solar powered:
A watch that uses solar energy (from any light source) to power the quartz movement.

stepping motor:
The part of a quartz movement that moves the gear train, which in turn moves the watch's hands.

stopwatch:
A watch with a seconds hand that measures intervals of time. When a stopwatch is incorporated into a standard watch, both the stopwatch function and the timepiece are referred to as a chronograph.

sub-dial:
A small dial on a watch face used for any of several purposes, such as keeping track of elapsed minutes or hours on a chronograph or indicating the date.

A-Z Index : T

tachometer:
(aka. "Tachymeter") A feature found on some chronograph watches, measures the speed at which the wearer has traveled over a measured distance. In watchmaking, a timer or chronograph with a graduated dial on which speed can be read off in kilometres per hour or some other unit (see "timer").

tank watch:
A rectangular watch designed by Louis Cartier. The bars along the sides of the watch were inspired by the tracks of tanks used in World War 1.

telemeter:
A telemeter determines the distance of an object from the observer by measuring how long it takes sound to travel that distance. Like a tachometer (see "tachometer"), it consists of a stopwatch, or chronograph, and a special scale, usually on the outermost edge of the watch face.

timer:
Instrument used for registering intervals of time (durations, brief times), without any indication of the time of day.

titanium:
A metal that is used for some watch cases and bracelets. Titanium is much stronger and lighter than stainless steel. Titanium is also hypo-allergenic.

tonneau watch:
A watch shaped like a barrel, with two convex sides.

A-Z Index : U

unidirectional rotating bezel:
An elapsed time rotating bezel (see "elapsed time rotating bezel"), often found on divers' watches, that moves only in a counterclockwise direction. It is designed to prevent a diver who has unwittingly knocked the bezel off its original position from overestimating his remaining air supply. Because the bezel moves in only one direction, the diver can err only on the side of safety when timing his dive. Many divers' watches are ratcheted, so that they lock into place for greater safety.

A-Z Index : V

vibration:
Movement of a pendulum or other oscillating element, limited by two consecutive extreme positions. The balance of a mechanical watch generally makes five or six vibrations per second (i.e. 18,000 or 21,600 per hour), but that of a high-frequency watch may make seven, eight or even ten vibrations per second (i.e. 25,200, 28,800 or 36, 000 per hour).

A-Z Index : W

water resistant:
A watch that is moderately waterproof & will withstand unexpected exposure to water for a very short time (such as splashes). Does not always mean the watch is submersible.

winding stem:
The button on the right side of the watch case used to wind the mainspring. Also called a "crown."

world time dial:
A dial, usually on the outer edge of the watch face, that tells the time in up to 24 time zones around the world. The time zones are represented by the names of cities printed on the bezel or dial. The wearer reads the hour in a particular time zone by looking at the scale next to the city that the hour hand is pointing to. The minutes are read as normal. Watches with this feature are called "world timers."