Glossary of Watch Terms

Alarm	The watch alerts you with beeps at pre-set time(s).
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).
Analog	A watch that shows the time using hour and minute hands.
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.
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.
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").
Built-in illumination	Lighting on a watch dial that allows the wearer to read the time in the dark. Check out Seiko's Lumi-brite technology.
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.
Case back	The plate on the back of the watch by which you can access the battery. Most case backs are stainless steel, but some are hard plastic. A screw-in case back is one that requires a special tool to "unscrew" the case back. This ensures a higher level of water resistance. You can tell if you have a screw-in case back by the "notches" (usually 5 or 6) around the circumference of the case back.
Chronograph	A watch that includes a built in stopwatch function - i.e., a timer that can be started and stopped to time 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 "tachymeter") 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.
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 as yacht races, where the sailor must maneuver the boat into position before the start of a race.
Crown	Also called a stem or pin, a crown is the 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.
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
Digital watch	A watch that shows the time through digits rather than through a dial and hands (analog) display.
Diving watch	A watch that is water resistant to 200M. Has a one-way rotating bezel and a screw-down crown and caseback. Has a metal or rubber strap (not leather). Has a sapphire crystal and possibly a wet-suit extension.
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.
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 fly back hand and the regular chronograph seconds hand in motion. To record a lap time or finishing time, stop the fly back 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.
Gear train	The system of gears which transmits power from the mainspring to the escapement.
Gold plated	A layer of gold electroplated to a base metal.
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, men's 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. For more information, visit Seiko's website.
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. The jewels reduce friction to make the watch more accurate and longer lasting.
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.
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.
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.
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.
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 (see elapsed time rotating bezel," "unidirectional rotating bezel," "bi-directional rotating bezel" and "slide rule.")
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.
Sapphire crystal	A crystal made of synthetic sapphire, a transparent, shatter-resistant, scratch-resistant substance.
Screw-down crown	A crown that can be screwed into the case to make the watch watertight.
Screw-in caseback	See "caseback."
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.
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 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. The Citizen >Solar-Tech< models use this technology and provide a 180 day power reserve, so they are able to run continuously. For more information, visit Citizen's website.
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.
Tachymeter	("tack IM eh ter") A feature found on some chronograph watches, a tachymeter (also called a "tachometer") measures the speed at which the wearer has traveled over a measured distance.
30-minute recorder (or register)	A sub-dial on a chronograph (see "chronograph") that can time periods of up to 30 minutes.
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.
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.
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.
Water resistance	The ability to withstand splashes of water. Terms such as "water resistant to 50 meters" or "water resistant to 200 meters" indicate that the watch can be worn underwater to various depths.
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."