ATM - the water pressure rating of a watch. ATM means atmosphere and is equal to 10 meters of depth. (1 meter = 3 feet)
1 ATM = 10 meters
5 ATM = 50 meters
Automatic watch – A watch that has the mainspring wound by the movement of the wearer's wrist rather than winding a stem.
Battery Reserve Indicator - EOL - end of life. Indicates pending battery failure.
One method of warning is to see the seconds hand jumping 2 seconds at a time
Bi-directional Rotating Bezel - a bezel that can be moved either clockwise or counter-clockwise. Used to make mathematical calculations or keeping track of elapsed time.
Carat - 1 carat = 1/24 of fine gold. 18 carat gold contains 18/24 fine gold or 75% gold content.
Case - the container that protects the watch movement. Cases can be made of different metals including stainless steel, gold, titanium, silver and platinum.
Caseback - the underside of a watch that lies against the skin. Some casebacks are made of crystal allowing you to view the watch movement.
Chronograph - watches with a built-in stopwatch function.
Chronometer - An instrument for measuring time very accurately. For a Swiss watch to be called a chronometer it must meet very high standards set by the C.O.S.C.
Countdown - time remaining in a predefined period.
Cousu Main - hand sewn. Found on well-made watch straps
Crown -A knob on the outside of the watch case used to wind the mainspring in mechanical watches
Cyclops - a small lens on the crystal to magnify the date.
Depth Alarm - alarm on a diver's watch that sounds when the wearer exceeds a pre-set depth. Alarm stops when the diver ascends above the pre-set depth.
Digital Display – Time is shown by using digits (numbers) instead of hands and a dial.
Direct Drive - the seconds hand advances in intervals rather than a smooth, sweeping motion.
Divers Watch - a watch that is specially constructed for underwater diving.
Dual-time-zone - A watch that measures local time as well as time in another time zone.
Eco-drive - a watch which operates on light (never needs a battery)
Ecomax - a low-battery warning system. The second hand is caused to jump at 2, 3 or 4 second intervals before the battery dies.
Engine Turning - decorative engraving
ETA - leading manufacturer in Switzerland for movements used in many Swiss watch brands.
Flange - The ring that separates the crystal from the dial.
Flyback Chronograph - A chronograph that can be stopped, reset and restarted with a single push of one button.
Full Rotor - Automatic watches with winding weights.
Gasket - most water-resistant watches are equipped with gaskets to seal the case-back, crystal and crown from water infiltration. Gaskets should be checked every couple of years to maintain water resistance.
G.M.T. Greenwich Mean time.
Goldplating - an electro deposited layer of gold. The thickness is measured in microns.
Hesalite - a brand name for a type of acrylic. Omega chose hesalite for the crystal on their Moon Watch because of its resistance to shocks and extreme temperatures.
Integrated Bracelet - A watch bracelet that is incorporated into the watch case
Isochronism –. A watch's ability to maintain it's rate as the mainspring unwinds.
Jewels - Bearings that are used in a watch movement to reduce friction. They are usually synthetic sapphires or rubies. They help to maintain the watch's lubrication with far less friction than metal.
Karat - indicates the purity of a metal on a scale of 24. 24K (24/24) indicates pure metal. Pure gold is too soft to use in jewelry so it is mixed with another metal. 18K gold means that the alloy is 18 parts gold and 6 parts some other metal.
18K - goldis also expressed as .750 (750/1000) or 75% pure.
14K - gold (.555) is 14 parts gold and 10 parts some other metal.
10K - gold (.425) is 10 parts gold and 14 parts some other metal.
Kif - a method of shock protection
Kinetic - A quartz movement that does not use a battery. Energy is stored for a period of time through movement of the wrist that charges a capacitor.
Lap Timer - a chronograph function that times segments of a race. At the end of a lap the push of a button stops the time and then returns to zero to time the next lap.
L.E.D. - Light Emiting Diode. Used in digital displays on electronic quartz watches.
Limited Edition - a watch style that has a limited number manufactured.
Luminescence - to emit rays of light. A luminescent material is deposited on numbers and hands in order to read the time in the dark.
Main Plate - the base plate on which all the other parts of a watch movement are mounted.
Mainspring - the driving flat-coiled spring of a watch or clock, contained in the barrel. Supplies power to the watch.
Manual-wind - a watch movement that must be wound manually every day or two to keep it running.
Manufacture - (Manufactory) a factory where watches are manufactured almost completely.
Marine chronometer - a highly accurate timepiece enclosed in a box that is used for determining the longitude on board ship. The marine chronometer is mounted on gimbals so that they remain in a horizontal position to maintain their precision.
Micron - 1/1000 mm. (0.001 millimetre). Used to measure the thickness of gold plating
Military time - time is measured in 24-hour segments
Mineral glass - ordinary glass that is used for windows. Mineral glass, even though it has been hardened by a tempering process, is more likely to break than Plexiglas. But it is also more scratch-resistant than Plexiglas.
Moon phase - shows what phase the moon is in by means of a disk that rotates beneath a small aperture. As the day of the month pass, one moon face indicates the phase of the real moon.
Movement - The engine of a watch. The machinery of any time piece that moves the hands and any complications.
Mineral Crystals - heat-hardened glass about 10 times harder than plastic.
Oscillating System - Two vibrations of the balance make the tick-tock sound of a mechanical watch known as one oscillation.
Oyster Case - a name given by Rolex for their water resistant watches.
Perpetual Calendar - a calendar complication that adjusts automatically for different month lengths and leap years. Perpetual calendars are programmed to be accurate until the year 2100.
Platinum - One of the rarest of precious metals as well as one of the strongest and heaviest. Platinum has a rich, white lustre and is hypoallergenic and tarnish resistant.
Plexiglas a clear, lightweight type of plastic. Plexiglas, as you would expect, is the least expensive. It is also the least likely to shatter and the most likely to become scratched.
Power reserve indicator - a subdial used to show how much power remains before the watch stops running.
Quartz Crystal - the tiny piece of quartz that serves as an oscillator in a quartz watch.
Rolled Gold - a thin sheet of gold bonded to a base metal
Ruby - Very hard stone, usually synthetic, that prevents the wear of the gear-train parts.
Sapphire Crystals - 2 - 3 times harder than mineral glass and virtually scratchproof. They are quite brittle so are more likely to crack or shatter than mineral.
Screw Back - The back of the case has a thread so that it can be screwed into the case.
Screw-down crown - a crown that screws down into the case to make the watch more water resistant and to help keep out dust.
Second time-zone indicator - an additional dial that can be set to the time in another time zone. It allows the wearer to keep track of 2 different time zones simultaneously.
Shock absorber - resilient bearing in a watch that is intended to take up the shocks received by the balance staff and protect it's delicate pivots from damage.
Shock Resistance - a watch's ability to withstand an impact equal to being dropped onto a wooden floor from a height of 3 feet.
Skeleton watch - the case, dial and various parts of the movement have been cut away allowing the main parts of the watch to be seen. A crystal is mounted on both the front and back of the watch
Stepping Motor - the part of a quartz movement that moves the gear train which in turn moves the watch's hands
Sterling silver - refers to silver that is 92.5% pure.
Swiss movement - a movement is considered to be Swiss if:
it has been assembled in Switzerland;
it has been inspected by the manufacturer in Switzerland; and
the components of Swiss manufacture account for at least 50 percent of the total value, without taking into account the cost of assembly.
Synthetic sapphire - is the most expensive glass crystal material and the most scratch resistant. A very hard, transparent material made of crystallizing aluminum oxide at very high temperatures. Chemically, synthetic sapphire is the same as the natural sapphire used in jewelry, but without the coloring. Because it is so hard, it is also brittle, and shatters more easily than mineral glass or Plexiglas. Sapphire (whether natural or synthetic) is one of the hardest substances on earth. It measures 9 on a scale of 10. Diamond is a 10.
Some crystals are made of both mineral glass and sapphire. Seiko, for example, makes some watches with crystals made of mineral glass covered with a layer of synthetic sapphire called "Sapphlex".
Tantalum - a grey, heavy, and very hard metal. Tantalum is used to make a variety of alloys a high melting point and high strength. Tantalum is completely immune to body liquids and is a non-irritating material.
Titanium - a metal, gray in color, that is used for some watch cases and bracelets. It is much stronger and lighter than stainless steel and is also hypo-allergenic.
Trimmer - found in expensive quartz movements. It is a variable capacitor that changes the frequency of the oscillator in order to advance or retard the rate of the watch.
Two-tone watch - a watch that is made up of two metals. Usually stainless steel and gold.
Uni-directional rotating bezel - A bezel that indicates elapsed time, often found on divers watches. It moves only in a counter-clockwise direction.
Vibration -A high frequency watch may make 7, 8 or 10 vibrations per second (25,200, 28,800 or 36,000 per hour). The higher the number of vibrations, the smoother the watch will run.
Waterproof - in most markets watches can not be described as waterproof. Watches must be marked as "water-resistant" followed by a depth rating.
Water resistant - ability to withstand water pressure. Made to prevent water from entering a watch. The watch case joints are made to prevent moisture from entering. Water resistance is measured in meters and refers to the depth that the watch will keep out water:
50 meters surface swimming
100 meters snorkelling
200 meters scuba diving (to 40 meters)
1,000 meters deep sea diving.
White gold - created from yellow gold by incorporating either nickel or palladium to the alloy.
75% Gold, 16% Palladium, 9% Silver
Yacht Timer - a countdown timer that sounds warning signals during the countdown to a boat race.
Yellow Gold - the traditional popular gold.
75% Gold, 10% Copper, 15% Silver.