Alarm function: A watch complication that allows the wearer to set an audible or vibration-based alarm at a specific time.

Amplitude: The degree of oscillation of the balance wheel in a mechanical watch, often measured in degrees and indicative of the watch’s overall performance.

Annual calendar: A watch complication that automatically adjusts the date for months with 30 or 31 days, requiring manual adjustment only for February.

Anti-magnetic: A watch designed to resist the effects of magnetic fields, which can affect the accuracy of a mechanical movement.

Automatic movement: A self-winding mechanical movement that uses the wearer’s motion to wind the mainspring, keeping the watch running.

Balance wheel: A crucial component in the escapement of a mechanical watch, the balance wheel oscillates back and forth to regulate the watch’s timekeeping.

Barrel: A cylindrical container in a mechanical watch that houses the mainspring, transmitting power to the gear train.

Bezel: The outer ring surrounding the watch dial, sometimes featuring markings or the ability to rotate for various functions.

Bracelet: A metal watchband consisting of interconnected links, offering a secure and often adjustable fit.

Bridge: A metal plate or bar that secures various components of a watch movement in place.

Caliber: Refers to the specific design or model of a watch movement, usually identified by a unique number or name.

Case: The outer protective housing of a watch that contains the movement, dial, and other components.

Case back: The rear cover of a watch case that protects the movement, often removable for servicing or battery replacement.

Chapter ring: A ring, often featuring markings or numerals, that encircles the watch dial and serves as a reference for timekeeping.

Chronograph: A watch complication that measures elapsed time, often with sub-dials for minutes and hours.

Chronometer: A highly accurate and precise mechanical watch that has undergone rigorous testing and certification, such as COSC certification.

Co-axial escapement: A type of escapement in a mechanical watch designed to reduce friction and increase accuracy, developed by watchmaker George Daniels.

Complication: Any additional function or feature of a watch beyond basic timekeeping, such as a date display or chronograph.

COSC certification: The Official Swiss Chronometer Testing Institute (COSC) certification, granted to watches that meet strict accuracy and precision standards.

Crown: The small knob on the side of a watch case used to set the time, date, or wind the watch.

Crystal: The transparent cover, usually made of sapphire, mineral glass, or acrylic, that protects the watch dial.

Deployant clasp: A folding clasp used on watch bracelets, designed for easy attachment and removal while providing added security when worn.

Dial: The face of the watch, featuring hands, indices, and other displays, used to indicate the time and any complications.

Digital watch: A watch that displays the time and other information through electronic digits, rather than analog hands.

Diver’s watch: A type of watch designed specifically for underwater use, featuring high water resistance and enhanced legibility.

Escapement: A mechanism in a mechanical watch that transfers energy from the mainspring to the balance wheel, regulating the watch’s timekeeping.

Exhibition case back: A transparent case back that allows the wearer to view the watch’s movement and its intricate components.

Finishing: The decorative techniques applied to watch components, such as polishing, engraving, or Geneva stripes, enhancing the watch’s aesthetics.

Flyback chronograph: A chronograph complication that allows the wearer to reset and restart the stopwatch function without stopping it first, improving timing efficiency.

Foudroyante: A watch complication that measures fractions of a second, often displayed on a separate sub-dial with a lightning-fast hand.

Frequency: The number of oscillations or vibrations per hour made by a watch’s regulating organ, typically expressed in hertz (Hz) or vibrations per hour (vph).

Gear train: A system of gears in a watch movement that transfers power from the mainspring to the escapement, driving the watch’s functions.

GMT function: A watch complication that displays a second time zone, often with an additional 24-hour hand, useful for travelers or tracking multiple time zones.

Hairspring: A thin, spiral spring that works in conjunction with the balance wheel to control the oscillations of the balance wheel.

Hack function: A feature in some mechanical watches that stops the second hand when the crown is pulled out, allowing for more accurate time setting.

Hand-wound movement: A mechanical watch movement that requires manual winding of the mainspring through the crown to store energy.

Horology: The study and science of timekeeping and the measurement of time.

Indices: The markers on a watch dial used to indicate hours or minutes, sometimes represented by numerals, lines, or other shapes.

Jewel: Synthetic rubies or sapphires used as bearings in watch movements to reduce friction and wear.

Jump hour: A watch complication that displays the hour numerically, with the hour “jumping” to the next hour as the minute hand reaches 60 minutes.

Lug: The part of the watch case that extends from the main body and attaches to the bracelet or strap.

Lume: Short for luminescence, a material applied to watch hands and indices that glows in the dark for improved visibility.

Mainspring: A coiled spring in a mechanical watch that stores and releases energy to power the movement.

Mechanical movement: A watch movement powered by a mainspring and regulated by a balance wheel and escapement, with no electronic components.

Micro-rotor: A compact, off-center rotor in an automatic watch movement that winds the mainspring, allowing for a thinner watch profile.

Minute repeater: A complex watch complication that audibly chimes the hours, quarter-hours, and minutes on demand, using a series of gongs and hammers within the watch.

Moonphase: A watch complication that tracks and displays the current phase of the moon on the dial.

Movement: The internal mechanism of a watch that powers its timekeeping and any additional complications.

NATO strap: A durable, one-piece watch strap, typically made of nylon or leather, designed for easy attachment and removal, often used in military or sports watches.

Pallet fork: A component in the escapement of a mechanical watch that interacts with the escape wheel and balance wheel, transferring energy and regulating timekeeping.

Perpetual calendar: An advanced watch complication that automatically adjusts for the varying number of days each month, including leap years.

Pinion: A small, toothed wheel in a watch movement that meshes with other gears to transfer power and motion.

Power reserve: The amount of time a mechanical watch will continue to run when fully wound, usually expressed in hours.

Pusher: A button located on the side of a watch case, typically used to control chronograph functions or to set calendar complications.

Quartz movement: A watch movement powered by a battery and regulated by the vibrations of a quartz crystal, offering high accuracy and low maintenance.

Rattrapante (split-seconds) chronograph: A chronograph with two second hands, allowing the wearer to time multiple events simultaneously or record split times.

Regulator: A component in a mechanical watch movement that adjusts the rate at which the balance wheel oscillates, ensuring accurate timekeeping.

Retrograde: A watch complication that displays a function (e.g., date, day, or power reserve) with a hand that moves along an arc and jumps back to the beginning when it reaches the end.

Rotating bezel: A bezel that can be rotated around the watch face, often used for tracking elapsed time or performing calculations.

Rotor: A weighted component in an automatic watch movement that rotates in response to the wearer’s motion, winding the mainspring.

Sapphire crystal: A synthetic sapphire material used for watch crystals, known for its high scratch resistance and durability.

Screw-down crown: A crown that can be screwed into the watch case to improve water resistance and protect the watch’s internal components.

Shock resistance: The ability of a watch movement to withstand impact and maintain accurate timekeeping, often achieved through the use of shock-absorbing materials and designs.

Skeleton watch: A watch with a transparent or partially transparent dial, showcasing the inner workings of the movement.

Solar watch: A watch that uses a solar cell to convert light into electrical energy, often eliminating the need for battery replacement.

Sub-dial: A smaller dial within the main watch dial, used to display additional information or complications, such as a chronograph or date function.

Swiss Made: A label indicating that a watch meets specific criteria for production, assembly, and quality control within Switzerland, often associated with high-quality timepieces.

Tachymeter: A scale, often found on the bezel or outer edge of a chronograph watch, used to measure speed based on time and distance.

Timekeeping: The process of measuring and displaying time in a watch, either through mechanical, automatic, or quartz movements.

Tourbillon: A complex and highly precise watch complication that counteracts the effects of gravity on a watch’s timekeeping by rotating the entire escapement.

Tritium: A radioactive isotope of hydrogen used as a luminescent material on watch hands and indices, providing continuous glow without exposure to light.

Two-tone: A watch design featuring a combination of two different metal colors or finishes, such as gold and stainless steel.

Water resistance: The ability of a watch to withstand exposure to water, typically expressed in meters or atmospheres (ATM). Not to be confused with waterproof, as no watch is truly waterproof.

Winder: A device used to keep automatic watches wound and running when not worn, mimicking the motion of the wearer’s wrist.

World timer: A watch complication that displays the time in multiple time zones, often using an additional hand or a rotating bezel.

Yacht timer: A watch complication designed for use in yacht racing, featuring a countdown timer for the start of a race, often with an audible or visual indication.

Zulu time: Another term for Coordinated Universal Time (UTC), often used in aviation and military contexts, displayed in some GMT or world timer watches.