Bezel: The ring that surrounds the watch crystal – usually metal, though it can be ceramic. On a dive watch the bezel often rotates, allowing the wearer to keep track of air supply.
Bracelet: Many watches have a metal bracelet in lieu of a leather, fabric, or rubber strap. An authorized jeweler can remove links from a new watch to ensure a perfect fit.
Buckle: A watch closure will come in one of two forms: either a deployant buckle, or an ardillon (or tang) buckle. A deployant buckle is the more secure of the two, in which a metal fixture allows for the watch to be loosened and put on or removed without completely opening. An ardillon or tang buckle, commonly used on a watch with a strap, is a belt-like closure.
Calendar: A complication that displays the date.
Case: The metal 'house' or watch head that contains the movement, dial, hands, and crown.
Caseback: The reverse side of the watch, which sits against your wrist. Sometimes, this is clear to show the movement inside – this is called an exhibition caseback.
Chronograph: A watch that features a stopwatch function.
Chronometer: A label only assigned to a timepiece after it has been tested by the Controle Officiel Suisse des Chronometeres (COSC) and meeting the precision standards of this official Swiss facility.
Crown: A small knob that attaches to the watch at 3 o'clock and allows the wearer to set the time and calendar function.
Crystal: The clear material that protects your watch dial. Frequently, the crystal is made from sapphire (either synthetic or natural) as this is is nearly scratch resistant.
Dial: The face of the watch, where you read the time.
Divers Watch: The minimum requirement for a watch to qualify as a divers watch is that it must be water resistant to a minimum of 100 meters, or roughly 330 feet.
Dual Time: A complication in which a watch has two hour hands, so that the wearer can keep track of two time zones at once. This function is popular with frequent travelers, as they can set one time to home time and the other to their destination time zone.
Fly Back Chronograph: A chronograph that automatically resets to zero and begins again when the second button is pushed. This differs from a normal chronograph, in which you need to stop, restart, and start the timer each time. This was developed for pilots who need split second accuracy. Sometimes this complication is referred to as 'retour-en-vol.'
Jewels: Rubies or sapphires (or their synthetic counterparts) that are used as bearings at the points of heaviest wear within a watch movement. These jewels reduce friction, and thus prolong the life of the watch movement.
Lugs: The 'arms' of the case so to speak, which attach to the strap or bracelet.
Moonphase: A complication that tracks the lunar cycle.
Movement: The mechanism inside your watch that keeps time (or more, if your watch has 'complications' – watch speak for other functionalities beyond displaying the time.)
Power Reserve: A feature on a mechanical watch that indicates how much longer the watch will function before it needs to be wound.
Pushers: Buttons on the side of the case of a watch that control complications.
Strap: A strap is often made from leather, but can also be made from rubber or fabric. Straps are adjustable in the same way one adjusts a belt – watches with straps do not need to be sized the way watches with bracelets do.
Tachymeter: A complication that measures speed based on time elapsed.
World Timer: A complication that indicates the time in all twenty-four time zones simultaneously.