A device that sounds a signal at a predetermined time.
A device that determines altitude by responding to changes in barometric pressure.
Amplitude: Maximum angle by which a balance swings from its position of rest.
A display that shows the time by using hands and a dial.
Anti-Magnetic: A watch that has been manufactured to resist becoming magnetized. (Watches that become magnetized may not keep accurate time because the magnetism interferes with the function of internal parts)
Aperture: Small opening in the dial, such as the ones used for displaying the day and date. In “jump hour” watches the Aperture will be used for displaying the time.
Arabic Numerals: 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 Roman Numerals I,II,III,IV,V,VI,VII,VIII,IX,X,XI,XII
Arbor: This is any post or axle that a moving part swings or rotates upon. Picture a gear with a post running through the center. That post/axle is called an “Arbor”.
Assembling: The process of putting together a watch. The assembly and manufacture of parts was formerly done entirely by hand but today are done by machine with inspection and timing for accuracy done by hand.
Automatic Watch: A watch that is wound by the everyday movements of the wearer. A tiny rotor turns and swings with whenever the watch is moved. This in turn rotating a tiny gear which ratchets the larger mainspring gear one click at a time. The system was invented in Switzerland by Abraham-Louis Breguet in the 18th century and was first used in a wrist-watch by John Harwood.
Auxiliary Dial: A smaller extra dial within the main dial. Example: Seconds dial.
A ring on your finger, or a group who plays music. When referring to watches, it is referred to as a bracelet or strap; not as a band.
The heart of a mechanical watch movement. The mainspring provides the energy and the balance (coupled with the hairspring) swings to divide time into equal parts.
A very small spring in a mechanical watch that returns the balance wheel back to its neutral position.
A part of a mechanical watch that oscillates and divides time into equal portions.
Largest watch show in the world. Held every year in April in Basel, Switzerland.
The ring around the crystal on the top portion of a watch. It is usually made of metals such as gold, gold-plate, platinum or stainless steel. It holds the glass or crystal in place.
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.
A Swiss word that refers to the high quality of a piece of work or an object. In French, it means “to make well”.
A feature that shows the day of the month, and often the day of the week. Some calendar watches show the date on sub-dials while others use a scale on the outside edge of the watch dial. (Learn more: Calendar Watches)
Also known as calibre, the caliber is the size or style of a watch movement.
The container that protects the watch movement. It also gives the watch an attractive appearance. Cases come in many shapes, round, square, oval, tonneau and rectangular.
The underside of a watch that lies against the skin. Some casebacks are made of crystal allowing you to view the watch movement.
A time that can be started and stopped to time and event. (Learn more: Chronographs)
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. (Controle Officiel Suisse des Chronometres). The requirements are 15 days and nights at five different positions and temperature changes.
Cotes de Geneve
A regular wave pattern obtained by engine-turning and polishing.
Time remaining in a predefined period.
A button, often fluted, on the outside of the watch case used to wind the mainspring in mechanical watches. It is also used to set the time, when pulled out, and for setting a watch calendar. A screw-down crown is used to make the watch more water resistant and to help keep out dust.
A transparent cover that protects the watch dial. Crystals are made of glass, plastic or synthetic sapphire. Non-reflective coatings on some crystals prevents glare. (See also: Mineral Crystals, Plastic Crystals, Sapphire Crystals)
A small lens on the crystal to magnify the date.
A watch that indicates the day of the week as well as the date. (Learn more: Date Complications)
A colored or shaded band on a world time watch, which shows the time zones that are in daylight and those in darkness.
A buckle that fastens to the watch strap and opens and fastens using hinged extenders. Invented by Louis Cartier in 1910. A deployant buckle is easier to put on and remove than a tang buckle. Deployant comes from the verb “deployer” which means to unfold. Do not mistakenly refer to it as a “deployment” clasp. This safety feature also ensures the watch won’t drop when putting it on your wrist.
In Italian, it translates to “right”. It means that the watch was intended to wear on the right hand, and is most commonly associated with Panerai timepieces.
A plate, with a metal base and visible through a crystal, that carries certain indication, such as the hours, minutes and sometimes seconds.
A watch that shows the time through a numerical display instead of via a dial and hands (analog watch).
A device in a mechanical watch that controls the motion of the hands by controlling wheel rotation.
The leading manufacturer in Switzerland for movements used in many Swiss brands.
In a chronograph, there is an additional seconds hand that moves with the seconds hand and can be stopped independently and then made to catch up (“fly-back”) with the other constantly moving seconds hand.
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. (Learn more: Watch Maintenance & Repair)
A system of gears that transmit power from the mainspring to the escapement.
Famous wave-like decorative pattern created on the bridges and oscillating weights of Patek Philippe watches. The tool required is crafted from boxwood by the craftsman, coated in abrasive paste, and then pressed manually in order to remove and extremely small amount of material and emboss the design.
Special alloy composed of copper, zinc, & 10% nickel. The nickel minimizes the oxidation of German silver and thus eliminates the need to electroplate, and remain “untreated”.
An electro deposited layer of gold with the thickness is measured in microns. “GP, HGE, GE” or any fraction after a number are stamps indicating gold plate.
Unauthorized sellers of new watches.
A repeater that sounds the hours and quarter hours by pressing a lever. (Learn more: Repeater Watches)
Greenwich Mean Time (GMT)
The standard for which all other 23 time zones are based off of and sometimes referred to as UTC. (Learn more: GMT Watches)
Surface decoration or texture. An even pattern is cut, usually on the dial.
The indicator that moves over the dial to point at the hour, minute or second. Watches generally have three hands to show the hours, minutes and seconds. Hands can have very different shapes: pear, Breguet, sword, skeleton, baton, arrow, etc.
Helium Escape Valve
Prior to surfacing from great depths in a pressurized enclosure, such as diving bell, toxic gases that have been formed in the enclosure are removed and helium is mixed into the air. The helium molecules are lighter than air and can therefore penetrate the watch. When the pressurized enclosure surfaces and is depressurized the helium rushes out of the watch so quickly that the glass on the watch pops out as well. The watch was built to withstand external pressure, not internal pressure. The glass popping out can be avoided by opening the Helium Escape Valve on the watch during resurfacing, which allows the helium to escape but prevents water from entering the watch.
The science of the measurement of time.
Arabic numerals, Roman numerals or symbols placed around the dial to mark the hours.
Hunter Pocket Watch
A pocket watch with a cover, which is distinguished by a winding stem at 3 o’clock.
Sapphire or Rubies that reduce friction by acting as bearings for gears in a mechanical watch.
Pocket watch without a cover, characterized by a winding stem at 12 o’clock.
Sometimes referred to as horns, lugs are projections on the watch case. There is a spring bar between the the lugs that is used to fix the strap or bracelet to the case.
Luminescence refers to emitting rays of light. A luminescent material is deposited on numbers and hands in order to read the time in the dark.
Contained in the barrel, the mainspring is the driving flat-coiled spring of a watch that supplies power.
A watch company that uses at least one of its own movements that has been manufactured in house.
Time that is measured in 24-hour segments. (IE: 10pm is referred to as 2200 hours).
Heat hardened glass about ten times harder than plastic. Extremely scratch resistant but must be replaced if they do scratch.
A mechanical movement is powered by a main-spring and works with the balance wheel.
The inner mechanism of a watch that keeps time and powers the watch’s functions.
Perlage, or circular graining, is cloud-like decoration on plates and bridges of the watch.
A calendar complication that adjusts the watch’s calendar for the varying length of months as well as leap years.
Plastic crystals are soft and flexible so they resist small impacts, enabling surface scratches to be buffed out.
Power Reserve Indicator
A feature of a mechanical watch that shows the remaining power in a watch movement, indicating the length of time until the timepiece will need to be wound again.
Physical vapor deposition is a thin coating applied to a case to add color for aesthetic purposes.
A movement that is powered by a quartz crystal. The crystal oscillates to power the timepiece.
Also referred to as Quick-Date, it is a mechanism to set the date directly to avoid having to turn the hands over 24 hours.
See “Split Seconds Chronograph”.
A part of the movement that makes time more accurate by regulating beats by speeding them up or slowing them down.
A device that chimes the time upon depressing a slide lever. (Learn more: Repeater Complication)
A hand with a tip moving over a portion of the arc of a circle instead of an entire circle. When it reaches the end of its path, it instantly returns to its point of departure.
Four markers placed around the bezel used as points of reference to mark a departure time or a set time one wishes to remember.
Part of an automatic watch that winds the mainspring by constantly rotating.
Sapphire crystals are 2-3 times harder than mineral glass and virtually scratch-proof. They are more brittle so are more likely to crack or shatter than mineral. Replacement cost is substantially higher than for mineral crystals.
The back of the case has a thread so that it can be screwed into the case.
A crown that screws down into the case to make the watch more water resistant and to help keep out dust.
Resilient bearing in a watch that is intended to take up the shocks received by the balance staff and protect its delicate pivots from damage.
A watch’s ability to withstand an impact equal to being dropped onto a wooden floor from a height of 3 feet.
The Salon International de la Haute Horlogerie (S.I.H.H.) is a trade show held each year in Geneva. New model watches are unveiled for the trade and the show is not open to the public.
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.
A rotating bezel that can multiply or divide two numbers, convert miles/KM, convert exchange rates, etc. An example is a dollar to Euro converter to calculate rate of descent or fuel consumption for pilots.
Small Seconds Dial
The seconds are displayed by a hand in a small subsidiary dial and not from the center of the timepiece.
A variation of a minute repeater that sounds the time automatically every hour (petite sonnerie) or quarter hour (grande sonnerie).
Split Seconds Chronograph
A watch that possesses two hands, one of which can be stopped to indicate an intermediate time while the other hand continues to run. (Learn more: Split Seconds Chronograph)
A spring loaded metal bar mounted between the case lugs (horns) used to attach a strap or bracelet.
The time that is kept locally in each of the time zones when it is not daylight savings time.
The shaft that connects to the movement’s winding mechanism. The crown is fitted on the opposite end.
A strip or band of leather or rubber that holds the watch to the wrist. It must be non-metal to be considered a strap; a metal version is referred to as a bracelet.
A small dial placed inside the main dial on a watch’s dial. Watches can have as many as four sub-dials (auxiliary dials). They give information not provided by the main watch dial such as chronographs, alarm, dual time zone, and calendar.
Sweeping Seconds hand
A second hand that is mounted in the center of the dial, instead of a sub-dial, and “sweeps” the entire dial of the watch.
A watch can only be considered to be Swiss made if, (1) its movement is Swiss; (2) its movement is cased up in Switzerland and (3) the manufacturer carries out the final inspection in Switzerland.
A tachometer, also referred to as a tachymetre, is a graduation on dial of a chronograph which enables one to determine average speeds or hourly production on the basis of an observation period of under sixty seconds.
Conventional feed through buckle (like a belt buckle).
Time zones refer to the twenty-four regions or divisions of the globe. Our time zone here in Minnesota will be indicated by either Chicago or Mexico City.
A tonque, or tang, is a movable metal piece in a buckle which penetrates the holes in a leather strap
A watch shaped like a barrel with two convex sides.
A device that eliminates errors in timekeeping by balance the horizontal and vertical positions of the balance wheel.
A slightly radioactive substance that collects light and is used to allow the hands or hour markers to glow in the dark. The radiation is so low that there is no health risk. Watches bearing tritium must be marked as such, with the letter T on the dial near 6 o’clock.
Uni-directional rotating bezel
A bezel that indicates elapsed time, often found on divers watches. It moves only in a counter-clockwise direction. If a diver is timing his remaining air supply and knocks the bezel by mistake, it can only move in one direction so that the error will only be on the side of safety.
The ability of a watch to withstand (resist) splashes of water on the timepiece. This will indicate the depth that a watch can be worn underwater.
Also referred to as a pinion, the wheel is a circular part that revolves around an axis to transmit power.
Winding is the action of tightening the mainspring of a watch. This is done by hand (turning the crown) or automatically (by the motion of the rotor).