Analog Watch: A watch with a dial, hands, and numbers or markers that presents a total display of a 12-hour time span. Analog digital refers to a watch that has both a digital display and hands of a conventional watch.
Automatic Movement: A mechanical movement that requires no winding because the rotor, part of the automatic mechanism, winds the mainspring every time you move your hand. The first automatic movement was invented in Switzerland by Abraham-Louis Perrelet in the Eighteenth century. When fully wound and left to sit, most automatics have up to 36 hours of reserve power. Mechanical movements are accurate within one minute each day. Automatic movements have gained in popularity the last few years especially with watch connoisseurs and are considered to be Switzerland’s mechanical answer to the popularity of the no-winding-needed quartz movements that are standard in Japanese watches.
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: (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 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.
Barrel: Thin cylindrical box containing the mainspring of a watch. The toothed rim of the barrel drives the train.
Bezel: The ring, usually made of gold, gold plate or steel, that surrounds the watch face.
Bi-directional Rotating Bezel: A bezel that can be moved either clockwise or counterclockwise. These are used for mathematical calculations or for keeping track of elapsed time.
Bracelet: A type of watch band made of elements that resemble links.
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.
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. Less expensive watches are usually made of brass and plated with gold or silver.
Caseback: The reverse side of a watch case that lies against the skin. May be transparent to allow viewing of the inner workings of the watch or be solid. Most manufacturers engrave casebacks with their name, water and shock resistance, case metal content and other details.
Chronograph: A stopwatch, 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 subdials to elapsed hours, minutes and seconds. Still others show elapsed time on a digital display on the watch face. 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. Some chronographs can time more than one event at a time. 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. Watches that include the chronograph function are themselves called “chronographs”.
Chronometer: This term refers to a precision watch that is tested in various temperatures and positions, thus meeting the accuracy standards set by an official institute in Switzerland. Most watch companies provide a certificate with your chronometer purchase.
COSC: The official Swiss Chronometer Testing Institute that puts every chronometer watch through a rigorous, 15-day testing procedure to verify the watch’s precision.
Crown: Button on the outside of the case that is used to set the time and the calendar, and, in the mechanical watches, to wind the mainspring.
Crystal: The transparent cover on the watch face made of glass crystal, synthetic sapphire or plastic.
Deployment Buckle: A type of buckle that pops open and fastens using hinged, often adjustable, extenders. Though more expensive than a belt-buckle like closure, a deployment buckle is easier to put on and remove and is more comfortable on the wrist.
Dial: The watch face. In high-end watches the numerals, indices and surface designs are applied as separate elements. In less expensive watches, they may be simply printed on the dial.
Digital watch: A watch that shows the time through digits rather than through a dial and hands 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. He/she can then read the elapsed time off the bezel. This saves him/her having to perform the subtraction that would be necessary if he 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.
Face: The visible side of the watch where the dial is contained. Most faces are marked with Arabic or Roman numerals to indicate the hours. Interestingly, when Roman numerals are used, it is traditional to use IIII, rather than IV, to indicate the 4 o’clock position.
Horology: The science of time measurement, including the art of designing and constructing the timepieces.
Index: An hour indicator on an analog watch dial, used instead of numerals.
Indiglo: A product feature on watches marketed by Timex, incorporating an electroluminescent panel as a backlight for even illumination of the watch dial. Click here for illustration.
Integrated Bracelet: A watch bracelet that is integrated into the design of the case.
Jewels: Synthetic sapphires or rubies that act as bearings for gears in the mechanical watch, reducing friction.
Jump Hour Indicator: A jump hour indicator takes the place of an hour hand. It usually shows the hours by means of a numeral in a window.
Liquid-Crystal Display: A digital watch display that shows the time electronically by means of the liquid held in a thin layer between two transparent plates.
Lugs: Projection on the watch face to which the watch band is attached.
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.
Manual Wind: A manual wind watch must be wound every day by the crown in order to run. Even with that inconvenience, they are still produced by the major houses in Switzerland. Some of the most beautiful pieces made today are manual wind, and you actually won’t find many value or budget manual winds (but they exist!). With exhibition backs becoming very common, it’s nice to view the active movement without a rotor in the way.
Mechanical Movement: A movement based on a mainspring which is wound by hand; when wound, it slowly unwinds the spring in an even motion. An automatic mechanical requires no winding because of the rotor, which winds the mainspring every time you move your wrist.
Movement: The inner mechanism of a watch that keeps time and moves the watch’s hand, calendar, etc. Movements are either mechanical or quartz.
Perpetual Calendar: A calendar that automatically adjusts for the months’ varying length and for leap year. Perpetual calendars, which can be powered by quartz or mechanical movements, are programmed to be accurate until the year 2100. Many watch collectors suggest storing mechanical versions in motorized winding boxes when they aren’t being worn in order to maintain the calendar countdown.
Power Reserve: The amount of energy reserve stored up to keep a watch running until it stops. The remaining power is sometimes indicated by a small gauge on the dial.
Power Reserve Indicator: A feature of a mechanical watch that shows how much longer the watch will operate before it must be wound again.
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 which allows a watch to keep time without being wound. This technology employs the vibrations of a tiny crystal to maintain timing accuracy. The power comes from a battery that must be replaced about every 1.5 years. In recent years, new quartz technology enables the watch to recharge itself without battery replacement. This power is generated via body motion similar to an automatic mechanical watch, or powered by light through a solar cell, or even by body heat. A digital quartz watch has no mechanical parts. Most quartz movements are made in Hong Kong, Japan or Switzerland.
Repeater: A device that chimes the time when the wearer pushes a button.
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 watch that winds the movement’s main spring.
Sapphire Crystal: A crystal (the cover that protects the watch face) 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.
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 the position and 12 o’clock, and turns the bezel until its “south” marker is at that halfway point. Some quartz watches have solar compasses that show directions on an LCD display.
Solar Powered Batteries: Batteries in a quartz watch that are recharged via solar panels on the watch face.
Swiss A.O.S.C. (Certificate of Orgin): A mark identifying a watch that is assembled in Switzerland with components of Swiss orgin.
Sweep Seconds-Hand: A seconds-hand that is mounted in the center of the watch dial.
Tachymeter: A device on the chronograph watch that measure the speed at which the wearer has traveled over a measured distance.
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 tachymeter, 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.
Tourbillon: A device in a mechanical watch that eliminates timekeeping errors caused by the slight differences 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. It rotates continuously at the rate of once per minute.
Tritium: An isotope of hydrogen that is used to activate the luminous dots or indices on a watch dial. The radioactivity released in this process is too slight to pose a health risk.
Two Tone: A watch that combines two metals, usually yellow gold and stainless steel in the case of fine watches.
Uni-directional Rotating Bezel: An 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 error only on the side of safety when timing his dive. Many divers’ watches are ratcheted, so that they lock into place for greater safety.
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).
Waterproof: An illegal and misused term. No watch is fully 100 percent waterproof.
Water Resistance: A water resistant watch can handle light moisture, such as rain 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, i.e. 50 meters or more on most sport watches. Below 200 meters, the watch may be used for skin diving and even scuba diving depending upon the indicated depths.
Winding: Operation consisting in tightening the mainspring of a watch. This can be done by hand (by means of the crown) or automatically (by means of a rotor, which is caused to swing by the movements of the wearer’s arm).
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 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”.