Analog-Digital Display (ana-digi): Watch that shows the time by means of hour and minute hands (analog display) as well as by numbers (digital display).

Arabic Numerals: Popular counterpart to Roman numerals consisting of 1,2,3, etc; Became popular during the 18th century and typically allow for more space on the dial for complications.

ATM: Commonly used measurement in water resistance; Stands for "atmospheres" or the amount of pressure a watch can withstand before leaking; One atmosphere is equal to 10 meters of water pressure.

Automatic Movement: Type of movement where the mainspring is wound via the movement of one’s own arm; Movement of the arm causes the rotor to rotate, which in turn winds the mainspring; Similar to mechanical movements, except winding is not manual.

Bezel: Retaining ring surrounding the case and securing the crystal; Sometimes incorporates unidirectional or ratcheting movements, as well as additional benefits such as chapter markers.

Case: Timepiece’s container; Protects the movement from dust, dampness and injury; Common case shapes are round, tonneau, rectangular and square.

Chronograph: Timepiece capable of both timekeeping and stopwatch functions; Chronographs are a unique and valued complication due to their ability to measure increments of time.

Chronometer: High-precision timepiece that has been tested and is certified to meet precision standards; Chronometer watches often come with certificates indicating their certified status.

Complication: Any feature added to the timepiece that does not indicate hours, minutes or seconds. Popular complications include chronographs, tachymeters, date windows and exhibition backs.

Crown: Small, cap-like device located on the side of a case that allows the user to set time or manually wind watch.

Crystal: Transparent cover on a watch face that gives view of the dial; Sapphire and mineral are the most common crystals used today.

Date Window: Reveals the numeric day of a given month.

Deployant: Type of clasp that keeps the closing mechanism hidden, creating an uninterrupted look for your bracelet or strap.

Dial: Plate beneath the crystal showcasing the timepiece’s features; Sometimes referred to as the face of a timepiece, the dial indicates hours, minutes and seconds, as well as complications such as date windows and sub-dials.

Dual Deployant: Similar to a deployant clasp, except it uses two hinges to fasten or open, as opposed to one.

Dual Time Zone: Timepiece that simultaneously gives time in two time zones.

Exhibition case: Unique complication wherein a crystal is implemented into the case back, allowing view of the timepiece's movement.

Greenwich Mean Time: Refers to the Royal Observatory in Greenwich, England where mean time is kept; Located at the prime meridian of the world, GMT is thought of as "the world's time".

Jewels: International term referring to the rubies, sapphires or other gemstones used as bearings in a watch movement; These bearings are set to reduce friction in a movement and help the delicate parts of the movement work smoothly and with great precision.

Mechanical Movement: Type of movement where the winding crown is used to power the movement; Needs to be manually wound after an elapsed period of time; Sometimes accompanied by a exhibition back to display its old-fashioned sensibilities.

Mineral Crystal: Technical term for glass; Standard crystal used in timepieces today.

Minute Repeater: Timepiece that sounds hours, quarters and minutes as requested.

Moon Phase: Complication on a timepiece that displays the various stages of the moon; Stages include new moon, first quarter, full moon and last quarter.

Mother-of-Pearl: Dial material that has been cultivated from the inside of certain shells; Provides an iridescent surface and gives timepieces a rich aesthetic.

Movement: Assembly making up the principal elements and mechanisms of a watch or clock; Includes the winding and setting mechanism, the mainspring, the train, the escapement and the regulating elements.

Perpetual Calendar: Complication that exhibits the days in a Gregorian calendar, the most common calendar used today; Automatically adjusts to months with different amounts of days in them.

Power Reserve: Time a watch will continue running based on the movement's residual winding of its mainspring; In quartz and digital watches, this can also refer to the amount of energy left in the battery.

Push Button Dual Deployant: Similar to deployant clasps, with the addition of two small hidden push buttons that spring your clasp open.

Quartz Movement: Most common type of movement used in modern timepieces; Vibrating at a high frequency and placed under an electric current, quartz movements provide accurate time without the need to wind.

Repeater: Complex watch mechanism that sounds hours, quarters or minutes, or repeats them on request; Originally designed to help the wearer to tell the time in the dark.

Retrograde: Hour, minute, second or calendar hand that moves across a scale and resets to zero at the end of its cycle.

Sapphire Crystal: High-end crystal that adds greater value to a timepiece; The only natural substance able to harm a sapphire crystal is a diamond.

Skeletonization: Cutting away unnecessary metal from the movement to allow the wearer to actually see through the movement; Any part that is not needed is carved out, leaving only the movement's skeleton.

Subdial: Smaller dials located on the main dial of a timepiece; Used to measure seconds, minutes or days.

Tachymeter: Popular complication that measures distance based on speed; Typically located along the outer rim of a dial.

Water resistant: Watches described as simply "water resistant" can handle light moisture, such as a rainstorm or splashes from a sink, but they should not be completely submerged in water for any length of time; A commonly used measurement in water resistance is ATM, which stands for "atmospheres" or the amount of pressure a watch can withstand before leaking.