In alphabetical order:
Automatic Watch
An automatic watch requires no battery. The watch mainspring is wound automatically by a balance wheel which rotates due to normal wrist motion whilst wearing the watch.There are 2 types of automatic watches i.e. mechanical and automatic. Mechanical watches have to be wound up and automatic watches work on the movement of the wrist.
Bezel
This is the ring around the case which holds the crystal of a watch to the case of the watch.
Bi-Directional Rotating Bezel
A bezel that can be rotated either clockwise or anticlockwise.
Buckle
The traditional loop and pin buckle is called a 'buckle'. A hinged fold-over style metal clasp that opens and closes easily, allowing the watch to be placed on the wrist.
Calendar
A feature that shows the date, and often the day of the week and month. Most calendar watches show the information digitally through an aperture on the watch face. If watches have perpetual calendars this will mean that the date will automatically change at the end of the month. Some chronograph watches show the information on sub-dials on the watch face.
Calibre
The mechanism inside the watch that tells the quality of the watch movement.
Case
A case of a watch is the primary housing for the internal watch movement.
Case back
The bottom of the watch case that can be opened for access to the watch movement for repair or battery change. Some watches have a sapphire glass backing which allows you to see the working mechanism of the watch.
Chronograph
This is a watch with a variety of extra features displayed on sub-dials to measure extra time, like a stopwatch. This can include hours, minutes, seconds or even days.
Chronometer
This is a watch which has been measured for accuracy and tested for precision by an official testing institute.
Complication
An additional function other than basic timekeeping of the hours, minutes, and seconds. Certain features such as automatic winding or date are considered complications. The main complications are power reserve, moon phase, GMT, and full calendars. Great complications are split second chronographs, perpetual calendars, tourbillons, and minute repeaters.
COSC
This is the Swiss Official Chronometer Testing Institute that will certify the official chronometer status of a watch.
Crown
The 'Crown' is known better as the adjustment dial on the watch. The crown is used to adjust the time, date and for winding up the watch.
Crystal
The 'crystal' is the transparent cover over the dial. The crystals can either be made from resin, minerals or sapphires.
Date Window
A small opening in the dial through which the date is displayed.
Deployment Buckle
The deployment buckle is a clasp that folds nicely in to the strap for elegancy.
Dial
The 'dial' is the face of the watch showing the time.
Diving Watch
A watch that is at least 200M water resistant. A diving watch has a one way rotating bezel and a screw-on crown and back. Some watches have a helium escape button to release the pressure after the diving.
Escapement
Set of parts (escape wheel, lever, roller) which converts the rotary motion of the train into to-and-fro motion (the balance).
End of Battery Life Indicator (EOL)
The EOL indicates when it is time to replace the existing battery. Different manufacturers use different methods to indicate a low battery, i.e. if a second hand usually sweeps, when the battery is low it will begin to tick.
Finishing
The finishing of watches come in three types of finishing's, a polished surface, a brushed finish and a gold plated finish.
Fly-Back Hand (Retrograde Date Hand)
Usually, a hand indicating a date or time against a scale and then 'flies back' to catch up with to another date or time. For example, a hand that 'flies back' to the beginning of the month after reaching the 28th, 29th, 30th, or 31st day of the month.
Geneva Stripes
A form of decoration in higher grade watch movements which look like a pattern on the face of the watch.
Grand Complication
A Grand Complication is a combination of complications but it must have a perpetual calendar with or without moonphase indication), a split-second flyback chronograph and a minute repeater. Manufactures quite often include many other complications as well.
Horological
The art of making a Timepiece.
Jewel
In watch making, a synthetic ruby used for making low friction bearing in which the delicate pivots of the movement wheels run in. In some deluxe watches, sometimes sapphires or garnets are used. Expensive watch movements are jeweled from the barrel to the balance, and all automatic work, date and complication movements are expected to be jeweled.
Luminous
The hour markers and/or hands have a feature coating of a glow in the dark which will illuminates in the dark so you can tell the time where there is insufficient light.
Manufacture
A French term for a watch factory which itself produces the components needed for the manufacture of watches.
Mechanical Automatic Wind
A watch which has mechanical moving parts and winds its mainspring automatically using an internal rotor system.
Mechanical Manual Wind
A watch which has mechanical moving parts and requires its mainspring to be manually wound.
Moon-Phase Calendar
On some watches, the display of the evolution of the lunar cycle: rising, full or waning moon.
Movement
This is the internal mechanism of a watch. Assembly of parts and main components such as the mainspring, balance assembly, escapement, train of wheels, setting and winding .
Perpetual Calendar
A complication or function of a watch which displays correctly without adjustment, the day, date and month, and can also account for leap year cycles.
Power Reserve Indicator
A 'Power Reserve Indicator' shows the power resource of a mechanical movement watch.
PVD (Physical Vapour Deposition)
A method of coating thin watch cases by integrating titanium particles and then depositing gold for color. (Usually comes in black finish)
Quartz
This is a watch with a battery-powered mechanism.
Rattrapante (double chronograph)
A watch with a double chronograph has two seconds hands. One hand is superimposed over the other. While one hand moves continuously, the other one can be stopped, started or reset to zero in order to estimate two separate events of different durations.
Repeater
A repeater is a complication in a mechanical watch or clock that audibly chimes the hours and often minutes at the press of a button. There are many types of repeater, from the simple repeater which merely strikes the number of hours, to the minute repeater which chimes the time down to the minute, using separate tones for hours, quarter hours, and minutes.
Retrograde
This is a pointer hand on a watch dial which returns to zero at the end of a prescribed period i.e. days/months. For example a watch may have a retrograde date, meaning that the hand moves up a scale a day at a time, pointing to the current date, when it reaches 31 it will spring back to 1.
Rotor
In automatic winding mechanisms, an unbalanced, semicircular metal turns freely in both directions winding the mainspring.
Sapphire Crystal
A Sapphire Crystal is a synthetic watch crystal that is extremely hard and very scratch resistant.
Skeleton Movement
Movement on a watch where the plates have been removed or trimmed so that you can see the gears and other parts.
Skeleton Watch
Crystal on the front and back.
Waterproof
No watch can be 100% waterproof.
Water Resistant
Describes a watch case designed to prevent water from entering.
Tachometer (Tachymeter)
A watch or stop watch used for the measurement of speed. It measures speed in kilometers per hour based on 1000m distance.
Tourbillon
This type of watch is a complex piece of micro-engineering which results in the escapement of a watch rotating on its own axis; the aim is to cancel out the variations in running regularity which can be caused by the watch being in different positions; (a watch may gain in one position yet lose in another).
Lexicon
