12-hour recorder:
A sub-dial on a chronograph that can time periods of up to 12 hours.

30-minute recorder:
A sub-dial on a chronograph that can time periods of up to 30 minutes.

Alarm:
A device that sounds a signal at a pre-set time.

Altimeter:
A device that determines altitude by responding to changes in barometric pressure.

Analog display:
A display that shows the time by means of hands and a dial.

Arabic Numerals:
Numbers on a watch dial that are written the way we typically write numbers.

ATM (atmosphere):
One atmosphere equals 33 feet. 1 ATM = 33 feet or 10 meters. 3.3 feet = 1 meter.

Auto repeat countdown timer:
A countdown timer that resets itself as soon as the pre-set time has elapsed and starts the countdown again. It repeats the countdown continuously until the wearer pushes the stop button.

Automatic winding:
(Also called “self-winding”) Winding that occurs through the motion of the wearer’s arm rather than through turning the winding stem. It works by means of a rotor that turns in response to motion, thereby winding up the watch’s mainspring. An automatic watch that is not worn for a day or two will wind down and will need to be wound by hand to get it started again.

Balance spring:
A very fine spring (also called a “hair spring”) in a mechanical watch that returns the balance wheel back to a neutral position.

Balance wheel:
The part of a mechanical watch movement that oscillates, dividing time into equal segments.

Baton markers:
Commonly referred to as stick markers, any straight-line marker used in place of numbers on a watch.

Battery:
The power source of a quartz movement. A typical battery will last 12 to 18 months.

Battery reserve indicator:
(also called end-of-life battery indicator) On a quartz watch it informs the wearer when the battery is low. Often this is indicated by the seconds hand moving at two or three-second intervals.

Beat:
One complete oscillation of the balance wheel. Measured in beats per hour, the higher the frequency, the more accurate.

Bezel:
The ring, usually made of gold, gold plate or steel that surrounds the watch face.

Bracelet:
A type of watchband made of elements that resemble links.

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

Calendar:
A feature that shows the day of the month and often the day of the week and the year. There are several types of calendar watches. Some show the date and day of the week with sub-dials and analog hands.

Caliber:
A watch movement.

Case:
The metal housing of a watch’s parts. Stainless steel is the most typical metal used but titanium, gold, silver and platinum can also be used.

Chronograph:
A malfunction sport watch with a stopwatch function. Most have two or three sub-dials or mini-dials, for measuring minutes and hours.

Chronometer:
A timepiece that has met certain high standards of accuracy set by an official watch institute in Switzerland.

Complication:
Additional mechanism such as strike train, chronograph and calendar, which can be made by only a few specialists.

Countdown timer:
A function that lets the wearer keep track of how much of a pre-set period of time has elapsed.

Crown:
Button on the outside of the watch case that is used to set the time and the calendar and in a mechanical watch, to wind the mainspring. In the latter instance, it is also called a “winding stem.”

Crystal:
The transparent cover on a watch face made of glass, crystal, synthetic sapphire or plastic.

Day/night indicator:
A colored or shaded band on a world time dial that shows which time zones are in daylight and which in darkness.

Deployment Buckle:
Type of hinged watch buckle that may be used on a leather strap or bracelet.

Depth Alarm:
An alarm on divers’ watch that sounds when the wearer exceeds a pre-set depth. In most watches, it stops sounding when the diver ascends above that depth.

Dial:
The face of a watch where the time is read.

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

Elapsed time rotating bezel:
A graduated rotating bezel used to keep track of periods of time. The bezel can be turned so the wearer can align the zero on the bezel with the watch’s seconds or minutes hand. The wearer can then read the elapsed time off the bezel.

Escapement:
Device in a mechanical movement that controls the rotation of the wheels and thus the motion of the hands.

Exhibition watch:
Any watch that allows the wearer to view the movement. Usually the back only, but occasionally both front and back are visible.

Face:
The visible side of the watch where the dial is contained. Most are printed with Arabic or roman numerals. Note: Traditionally IIII, rather than IV, is used to indicate the 4 o’clock position.

Fluted bezel:
A type of grooved, high polish bezel.

Fly-back hand:
A second’s hand on a chronograph that is used to determine lap or finishing times for several competitors. To operate, put both the flyback and the regular second hand in motion; then to record a lap or finish time, the flyback hand can be stopped. After taking the results, push a button and the flyback hand will catch up to the constantly moving second hand.

GMT(Greenwich Mean Time) :
A watch that keeps track of two or more time zones, usually with an extra hour hand that travels once around the dial every 24 hours, and is read on the bezel rather than the dial.

Galbee:
The formal name of a watch with a curved case and movement. Sometimes called curvex.

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

Hands:
The parts of any analog watch that point to the hour, minute or seconds markers. The most common types of hands are sword, baton, dauphine and brueget.

Horology:
The science of time measurement, including the art of designing and construction timepieces.

Index:
The hour indicator on an analog watch, used instead of numerals. (Also referred to as markers.)

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

Jewels:
Synthetic sapphires or rubies that act as bearings for gears in a mechanical watch, reducing friction. A quality hand-wound or automatic mechanical timepiece contains at least 17 jewels.

Jump hour indicator:
A jump hour indicator takes the place of an hour hand. It shows the hour by means of a numeral in a window on the watch face.

Lap memory:
The ability, in some quartz sport watches, to preserve in the watch’s memory the times of laps in a race that have been determined by the lap timer. The wearer can recall these times on a digital display by pushing a button.

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.

Leap Year indicator:
Usually in perpetual calendar watches, this tells the wearer when it is leap year. The most common execution of this complication is to show the Roman numeral I, II, III or IV in a window with IV representing the leap year.

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

Lugs:
Extensions on either side of the bezel where the bracelet or strap is attached.

Mainspring:
The power source of a mechanical watch. A long strip of metal that drives the movement with the energy of its uncoiling.

Manual Wind:
The simplest type of mechanical movement. The wearer manually rewinding the crown maintains the mainspring tension. It is best for the watch to be wound at the same time each day.

Manufacturer:
A company that designs and makes entire watches.

Mechanical movement:
A movement powered by a mainspring, working in conjunction with a balance wheel (as opposed to a battery and quartz crystal).

Mineral crystal:
A heat or chemical treated type of glass crystal. Generally, these cannot be polished.

Minute repeater:
A complication on a watch that can strike the time in hours, quarters, or seconds by means of a push piece. The first complication invented, before electricity, was in 1687 by Daniel Quare to enable the wearer to tell time in the dark. Moon phase: A window in a watch face that shows which phase the moon is in. A disk beneath the window, painted with two pictures of a moon, rotates as the month progresses, revealing gradually larger or smaller segments of the picture.

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

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 automatically adjusts for the months’ varying lengths and for leap years.

Plastic crystal:
The least expensive type of watch crystal, these are easily scratched, but also easily polished.

Plate:
A watch has a front and back plate or a top and bottom plate, with the works found in between.

Power reserve indicator:
A feature of a mechanical watch that shows how much longer the watch will operate before it must be wound.

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:
A movement powered by a vibrating quartz crystal.

Repeater:
A striking watch in which the train can be actuated at will by the wearer to sound off the hours in some, also the quarters, minutes or half-quarters.

Reserve:
Running time of a watch after it has been fully wound.

Retrograde Calendar:
A scale on the outer rim of the watch face, numbered from 1 to 31. A hand then points to the date.

Reveil:
A mechanical alarm watch.

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 (elapsed time bezel, uni-directional, bi-directional and slide rule).

Rotor:
The part of an automatic, or self-winding, 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.

Sapphire crystal:
A crystal (the cover that protects the watch face) made of synthetic sapphire, a transparent, shatter-resistant, scratch-resistant substance. It is nine on the hardness scale. Because it is so hard, it is brittle and in some instances may shatter.

Screw-down crown:
A crown that can be screwed into the case to make the watch watertight.

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 case:
A case with a transparent front or back that allows the wearer to view the watch’s movement.

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.

Solar compass:
A compass that lets the wearer determine the geographical poles by means of a rotating bezel. The wearer places the watch so that the hour hand faces the sun. He then takes half the distance between that position and 12 o’clock, and turns the bezel until its “south” marker is at the halfway point.

Split function:
Used to time a single event and all of its parts (going from point A to point C, this would allow you to time A and B, B and C, as well as A and B and C).

Split seconds hand:
Actually 2 hands, one a flyback hand, the other a regular chronograph hand. When the wearer starts the chronograph, both hands move together. To time laps or different finishing times, the wearer can stop the flyback hand independently while the regular chronograph hand keeps moving, in effect splitting the hands in two.

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

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

Sweep seconds-hand:
A seconds-hand that is mounted in the center of the watch dial.

Swiss Made:
A watch is considered Swiss if its movement was assembled, started, adjusted and controlled by the manufacturer in Switzerland.

Tachymeter:
Probably the most common additional feature on a chronograph watch. A tachymeter (also called a tachometer) measures the speed at which the wearer has traveled over a measured distance.

Totalizer:
A mechanism that keeps track of elapsed time and displays it, usually on one sub-dial or several sub-dials on the watch face. Same as a “recorder” or “register” The term totalizer can be used more generally to refer to any counter on a watch, such as a stroke counter on a golf watch.

Tourbillon:
A device in a mechanical watch that eliminates timekeeping errors caused by the slight difference in the rates at which a watch runs in the horizontal and vertical positions. The tourbillon consists of a round carriage, or cage, holding the escapement and the balance. As it rotates continuously at the rate of once per minute. It was invented in 1801 by Abraham Brequet. In simple terms, it nullifies gravity’s effect on the watch.

Water proof:
An illegal and misused term. No watch is fully 100% waterproof.

Water resistance:
A watch bearing the inscription “water-resistant” on its caseback can handle light moisture, such as a rainstorm or sink splashes, but should not be worn swimming or diving. If the watch can be submerged in water, it must state at what depth it maintains water-resistance.

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

Yacht timer:
A countdown timer that sounds warning signals during the countdown to a boat race.