Altimeter: A function that provides altitude by responding to changes in barometric pressure, commonly found in pilot watches. note that inside a pressurized airplane cabin, the altimeter will register as if on land.

Analog digital: A watch that has both a digital display and hands of a conventional watch. usually featured on sport watch styles.

Analog watch: A watch with a dial, hands, and numbers or markers that present a total display of a 12-hour time span.

Atomic time standard: Provided by the United States National Institute of Standards and Technology, Time and Frequency Division, Boulder, Colorado, atomic power. Mechanical movements are accurate within one minute each day.

Bezel: The surface ring on the watch that surrounds and holds the crystal in place. A rotating ratchet bezel moves in some sport watches as part of the timing device. If rotating bezels are bi-directional, able to move clockwise or counter clockwise, they can assist in calculations for elapsed time.

Bracelet: A type of watch band made of elements that resemble links.

Cambered: Often used in referring to a curved or arched dial or bezel.

Case: The metal housing of a watch’s parts. Stainless steel is the most typical metal used but also titanium, gold, silver, and platinum can be used. Less expensive watches are usually made of brass and plated with gold or silver.

Chronograph: A multifunction sport watch with a stopwatch function. Most have two or three subdials, or minidials, for measuring minutes and hours.

Chronometer: A precision watch that is set in various temperatures and positions, thus meeting the accuracy standards set by an official watch institute in Switzerland. Most watch companies either provide this certificate with a purchase or it can be mailed to you.

Complication: A watch with other functions besides timekeeping. For example, a chronograph is a watch complication. Other complications coveted by watch collectors include: minute repeater, tourbillon, perpetual calendar, or split second chronograph.

Crown: Nodule extending from the case that is used to set the time, date, etc. Most pull out to set the time. In water-resistant styles, the crowns should screw down.

Crystal: The clean cover over the watch face. Three types of crystal are commonly found in watches. Acrylic crystal, a plastic, is inexpensive and shallow scratches can be buffed out. Mineral crystal is comprised of several elements that are heat treated to create unusual hardness that aids in resisting scratches. Sapphire crystal is the most expensive and durable, approximately three times harder than mineral and 20 times harder than acrylic crystals. A non reflective coating on some sport styles prevents glare.

Day/date watch: A watch that indicates not only the date but the day of the week.

Dial: The watch face. The numerals, indices, or surface design are usually applied; others have been printed on.

Dual timer: A watch that measures current local time as well as at least one other time zone. The additional time element may come from a twin dial, extra hand, subdials, or other means.

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.

Flyback hand: A seconds 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 finishing 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.

Guilloche: A style of intricate engraving that is popular on watch dials, usually very thin lines interwoven to create a surface texture.

Hard metal: A scratch-resistant metal comprised of binding several materials, including titanium and tungsten-carbide, which are then pressed into an extremely hard metal and polished with diamond powder to add brilliance.

High-tech ceramic: Used as a protective shield for spacecraft reentering the earth’s atmosphere, high-tech ceramic is polished with diamond dust to create a highly polished finish. Because the ceramic can be injection molded, pieces can be contoured. It has a very smooth surface, usually found in black, but can be produced in a spectrum of colors.

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

Index: The hour indicator on an analog watch, used instead of numerals.

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

Lighted dials: Several types of lighted dials are used so that you can tell time in the dark. Recently, a patented night-lit process, called electro-luminesce, lights the entire dial with uniform light that makes for easy reading in nighttime situations. A side button activates the light. This technology often appears under a brand name such as Timex’ Indiglo or Seiko’s LumiBrite.

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

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 body.

Military or 24-hour time: When time is measured in 24-hour segments, to convert 12-hour time into 24-hour, simply add 12 to any p.m. time. To convert 24- hour time into 12-hour time, subtract 12 from any time from 13 to 24.

Minute repeater: A complication on a watch that can strike the time in hours, quarters, or seconds by means of a push piece.

Moon phase: An indicator that keeps track of the phases of the moon. A regular rotation of the moon is once around the earth every 29 days, 12 hours, and 44 minutes. Once set, the moon phase indicator accurately displays the phase of the moon.

Mother-of-pearl: Iridescent, milky interior shell of the freshwater mollusk that is sliced thin and used on watch dials. While most have a milky white luster, mother-of-pearl also comes in other colors such as silvery gray, gray blue, pink, and salmon.

Movement: The inner workings or assembly that make up the main timekeeping mechanism. Movements are either quartz or mechanical.

Perpetual calendar: A complication that indicates leap years as well as the date.

Platinum: One of the rarest of precious metals, platinum also is one of the strongest and heaviest, making it a popular choice for setting gemstone jewelry and watches. It has a rich, white luster, and an understated look. Platinum is hypoallergenic and tarnish resistant. Platinum used in jewelry and watches is at least 85 to 95 percent pure. Many platinum watches are produced in limited editions due to the expense and rarity of the metal.

Quartz crystal movement: A movement which allows a watch to be worn without being wound. This technology employs the vibrations of a tiny crystal to maintain accuracy of time. A digital quartz watch has no mechanical parts but is powered by a battery. The cell battery must be replaced about every 1.5 years. Numbers and letters are on a Liquid Crystal Display (LCD). Most quartz movements are made in Hong Kong, Japan, or Switzerland.

Rose (or pink) gold: A softly hued gold that contains the same metals as yellow gold but with a higher concentration of copper in the alloy. A popular color in Europe, rose gold in watches is often seen in retro styling or in tricolor gold versions. Some 18k red gold watches achieve their color from additional copper in the alloy.

Shock resistance: If shock resistance is specified on a watch case, a watch can withstand normal wear and tear, even during strenuous sport activities.

Skeleton case: A transparent front or back that permits viewing into the inner workings of the watch.

Solar-powered: A type of quartz movement where the batteries are recharged via solar panels on the watch face. They have a power reserve so they can run even in the dark.

Split-second: A feature on a chronograph that actually is two hands, one a flyback, the other a regular hand. To time laps or different finishing times, the wearer can stop the flyback hand independently while the regular hands keep moving — in effect splitting the hands in two.

Stainless steel: An extremely durable metal ally (chromium is a main ingredient) that is virtually immune to rust, discoloration, and corrosion; it can be highly polished, thus resembling a precious metal. Because of its strength, stainless steel is often used even on casebacks on watches made of other metals.

Sterling silver: A white and highly reflective precious metal. Sterling refers to silver that is 92.5 percent pure, which should be stamped on the metal, sometimes accompanied by the initials of a designer or country of origin as a hallmark. Although less durable than stainless steel and other precious metals, sterling silver if often employed in watches that coordinate or look like sterling jewelry. A protective coating may be added to prevent tarnish.

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

Sweep seconds-hand: A seconds-hand mounted in the center of the dial instead of a subdial.

Tachymeter (also tachometer): A watch function that measures the speed at which the wearer traveled by means of a numerical scale on the watch bezel of a chronograph. Frequently used to determine a speed of a car over a measured distance.

Tank watch: A rectangular watch with heavier bars on either side of the dial, inspired by the tank tracks of World War I and first created by Louis Cartier.

Telemeter: A watch function that finds the distance of an object from the wearer by measuring how long it takes sound to travel that distance. Like a tachymeter, a telemeter consists of a stopwatch function and a special scale on the dial of a chronograph.

Titanium: The “space age” metal, often with a silver-gray appearance. Because it is 30 percent stronger and nearly 50 percent lighter than steel it has been increasingly used in watchmaking, especially sport watch styles. Its resistance to salt water corrosion makes it particularly useful in diver’s watches. Since it can be scratched fairly easily, some manufacturers use a patented-coating to resist scratching.

Tonneau watch: A watch with a barrel-shaped case with two convex sides.

Tourbillon: A device in some mechanical watches that eliminates timekeeping errors caused by slight variations due to shifts in gravity when a watch changes position during use. The round carriage or “cage” of the tourbillon holds the mechanisms that rotate the wheels, and thus the hands of the watch, in a continuos rate of once per minute.

Waterproof: An illegal and misused term: No watch is fully 100 percent waterproof.

Water resistant: A watch bearing the inscription “water-resistant” on its caseback can handle light moisture, such 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, i.e. 50 meters (165 feet) 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. Sonmethimes water-resistance is measured in atmospheres (ATM), which is equal to 10 meters of water pressure. (Some European-made watches use the term “bar” instead). Straps other than metal bracelets may not be water-resistant. new water- resistant versions of nylon, rubber, and other synthetics are a trend in sport watches.

White gold: Created from yellow gold by incorporating either nickel or palladium to the alloy to achieve a white color. Most watches made of white gold will be 18k.

World timers: A watch with a dial that indicates up to 24 time zones around the world, usually found on the outer edge of the face or sometimes on the bezel. Time zones around the world are indicated by major cities.

Yellow gold: The traditionally popular gold used in all gold or gold and stainless steel or other precious metal combinations. Yellow gold watches may be found in 14k or, as found from most European manufacturers, 18k.