A/h – A unit of measurement, alterations per hour, in reference to the frequency of the watch movement.
Alarm – Allows a watch to make noise or vibrate at a pre-set time.
All or nothing piece – A timepiece that won’t ring the hours if insufficiently wound.
Altimeter – Allows a watch to measure altitude, including ascent and descent. Useful for climbers, divers and flyers
Amplitude – The amount of swing in the rotation of the balance wheel, measured in degrees. An inconsistent amplitude may indicate an issue with the movement.
Anadigi display – A watch display that combines both analogue and digital, having both hands and a numerical read out.
Analogue – A traditional watch display with a dial and hands.
Anglage – Having angled or bevelled components within the movement itself, usually at 45 degrees.
Antimagnetic – Magnetic fields can interfere with watch movements, making them slow. An antimagnetic watch resists this effect by having non-magnetic components or an insulating case.
Aperture – A small opening within the watch face to display time or date.
Arabic numerals – 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 are the Arabic numerals.
Atomic clocks – A timepiece that uses radiation to regulate its frequency. Where most time pieces are accurate within a few seconds per day, Atomic Clocks can be accurate to nanoseconds across thousands of years.
Auto repeat countdown timer – A timer that allows itself to reset and repeat after a predetermined time has elapsed.
Automatic watch – A watch with a mechanical movement with an oscillating weight which winds the mainspring as the watch is moved.
Automatic winding – Any form of winding that is performed by the watch, usually due to the watch being moved by the wearer. A self-winding watch may run down if not moved for a day or two and require manual restart.
Balance – The regulating assembly consisting of the hairspring, escapement and balance wheel which rotates on its axis back and forth at regular intervals, creating the familiar tick-tock sound.
Balance spring – A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulates the timekeeping. This is also known as the hairspring.
Balance wheel – The part of a mechanical watch movement that oscillates, dividing time into equal segments. This is the regulating mechanism that controls the watch’s timekeeping accuracy.
Bar – A unit of measurement of a watch’s water resistance. 1 bar is approx. 10m depth resistance.
Barrel – A drum that holds the mainspring in a mechanical watch. The toothed rim of the barrel drives the train.
Beat – A single vibration of the movement, sometimes called a semi- or half-oscillation.
Bevelling – Bevelling is the act of transforming a square edge into a sloped one by filing down the corner. It is often used on watch movements to save space.
Bezel – The ring on the outside of the watch case, around the dial, or the rim that holds the watch glass. It may have calibrated markings, especially on sports or divers watches. (A Bi-directional rotating Bezel can be used to track time by rotating back and forwards.)
Bracelet – A metal strap made of separate links to allow size adjustment by adding or removing links.
Bridge – A part that is fixed to the main plate to form the frame of a watch movement. All other parts are mounted inside the frame.
British-made – A watch can only be said to be British-made if 50% of it was assembled, started, adjusted and controlled by the manufacturer in Britain.
Calendar – Allows the watch to record the day of the month and sometimes week and year.
Cambered – An arched or curved dial or bezel.
Calibre – The model reference of the watch movement.
California dial – A style of arranging the information on a dial with split typography, usually Arabic and Roman numerals, for easy reading with short glances.
Case – The metal housing that contains a watch’s parts. Stainless steel is most commonly used although titanium, platinum, gold and silver can also be found. Less expensive watches are often made of brass and plated with gold-coloured or silver-coloured metals.
Centre sweep seconds hand – Where the seconds hand is mounted alongside the hours and minutes in the centre of the dial, as opposed to on a separate sub-dial.
Chapter ring – A style of arranging the information on a dial with a large outer ring for the hours.
Chimes – The gongs or bars that when struck by hammers create a noise to signal the time, commonly found in minute repeaters.
Chronograph – A watch that tells the time and acts as a stopwatch. The timing element can be stopped and started without interfering with the ability to tell the time. There are many different types. Some have a centre seconds hand which keeps time on the watch’s main dial. Some use smaller subsidiary dials or a digital display to show elapsed time. A chronograph used in conjunction with specialized scales on the watch face can determine speed and distance. Some can time more than one event at one time.
Chronometer – A watch that has been vigorously tested in various positions and temperatures to ensure that it meets high standards of accuracy demanded by the COSC, the official Swiss chronometer testing institute. To be called a chronometer, the mechanical movement must achieve an average rate of between -4/+6 seconds per day.
Clepsydra – Sometimes called a water clock, it measures time using the flow of liquid such as water or mercury.
Clous de Paris – A style of guilloché, a hobnail pattern that looks pretty.
Column wheel – An upright wheel found in some chronographs that operates the levers to control the chronograph function, turning it on and off and resetting it to zero.
Complication – A watch function other than timekeeping. These include chronograph, perpetual calendar, tourbillon and minute repeater. A watch with any additional function is called a complicated watch.
COSC – COSC (Contrôle officiel suisse des chronomètres) controls the official registration of watches as Chronometers.
Côte de Genève – A style of guilloché, bars that keep dust from reaching the movement.
Countdown timer – Allows the watch to countdown a pre-set amount of time, sometimes with a sound warning.
Crown – The grooved button on the outside of the case, used for setting the hands on a watch, and the day and date, where applicable. It is also used for winding the mainspring of a manually wound watch.
Crystal – Clear cover on the watch face designed to protect the dial, can be made of many materials including glass, plastic, and crystal.
Cuvette – An inner dust cover on a watch case.
Day/Date – A watch that can display day/date.
Day/Night indicator – A coloured or shaded band on a world time that shows which time zones are in daylight and which are in night-time.
Damaskeening – A type of decorative etching on the movement.
Deployment buckle – This refers to two curved strips of hinged metal on a watch with a strap that fastens the strap tightly to the wrist. It tends to be a feature of quality watches.
Deployment clasp – See. deployment buckle, but on a bracelet strap.
Digital display – A watch that shows the time in numbers, or digits, rather than hands and a dial. Liquid crystal display (LCD)is commonly used.
Divers watch – An iconic watch archetype designed for use in and around the water for swimming, diving and sometimes sailing. Its key features include high water resistance, good legibility underwater and a unidirectional rotating bezel.
DLC – DLC or Diamond-like carbon (coating) is a harder than steel coating that can be applied to the metal of a watch case to make it even more durable and resistant to scratches.
Dual timer – A watch that can show the time both locally and in at least one other time zone.
Duo display – See. Anadigi display. A display with analogue and digital features.
Dial – The face of the watch, showing the time.
Ébauche – An unassembled movement.
Elapsed time rotating bezel – A graduated rotating bezel that is used to keep track of periods of time. The bezel can be rotated so the wearer can align the zero of the bezel with the watch’s minutes or seconds hand. The elapsed time can then be read off the bezel, rather than the wearer having to perform a subtraction necessary if they used the watch’s regular dial.
EOL – An indicator that signals the end-of-life for a quartz battery in a watch.
Engine Turning – This is a centuries-old craft that, today, involves the use of antique machines to engrave delicate patterns on metal watch components, including cases, dials, bezels and movements. It is also known as guilloché.
Escapement – The device in a mechanical movement that releases energy from the mainspring to control the rotation of the balance and ultimately move the hands.
Field watch – Field watches are a watch archetype designed for military use, first being used widely in WWII. Their key features are high accuracy to allow for coordinated manoeuvers and high durability to resist the wear and tear of combat.
Flyback hand – A seconds hand on some chronograph watches that can be used to time laps or determine the finishing times for several race competitors. It is also known as rattrapante.
Frequency – The number of vibrations a watch makes in a set time, a modern mechanical watch is usually 21,000-28,800Hz but a quartz watch can go much higher.
Function – See. complications.
Gear train – The system of gears which transmits power from the mainspring of the watch to the escapement.
GMT (Time zone) – Short for Greenwich Mean Time, the time zone from which all other time zones are measured.
GMT (Function) – When a watch has a second time zone function, it is sometimes called a GMT function.
Grand complication – A watch with at least three complications/functions in addition to timekeeping.
Guilloché – A type of engraving that can be cosmetic or functional. It is achieved through a technique called engine turning and there are multiple styles such as Côte de Genève and Clous de Paris.
Hacking seconds – A seconds hand which can be stopped by pulling the crown out, allowing for easier synchronisation with another timepiece or precise measurements of time.
Hairspring – See. Balance spring. A very fine spring that regulates timekeeping.
Hands – Hands are the primary method of telling the time on analogue watches. They point to the numerals or indices around the edge of the face to indicate the time. There are lots of designs and styles used, some popular ones are the sword design and leaf design.
Horology – The science of time measurement, encompassing the art of designing and constructing watches.
Index (sing.) and Indices (plur.) – The hour indicators on an analogue watch dial, used in place of numerals. Typically found around the edge of the dial, engraved or applied.
Integrated bracelet – A bracelet that is shaped and attached to the case of a watch in such a way that it appears to be part of the watch, with the lines of the case smoothly continuing into the bracelet.
Jewels – Synthetic gemstones that act as bearings for the gear trains, reducing friction and wear. They are typically rubies, the third hardest gem after diamonds and sapphires.
Lap timer – A function in a chronograph watch that allows the wearer to time segments of a race. At the end of a lap, the timer is stopped and then returns to zero to begin timing the next segment.
Lever escapement – A method of changing the settings on a watch that doesn’t require a crown, so is less likely to be adjusted by accident. Historically used on trains to avoid timetable errors.
Ligne – A type of measurement sometimes used for the diameter of a movement, equivalent to 2.256mm
Liquid crystal display – Liquid crystal display (LCD) watches show a numeric display continuously by means of the liquid held in a thin layer between two transparent plates. The numbers are made up from seven segments that form the number 8 when all are activated. They are activated by an electronic impulse.
Lugs – The arms of the watch case that hold the strap or bracelet.
Lume – Also known as SuperLuminova, is a luminescent substance commonly applied to watch faces and hands. It requires exposure to sunlight to glow and is not as bright as alternative substances but is more commonly used as it is not radioactive.
Main plate – The base plate upon which all other parts of a watch movement are mounted.
Mainspring – The coiled spring which provides the power to drive a mechanical watch movement and directly impacts the power reserve.
Manual – A mechanical watch that requires winding by an external force in order to keep time, such as a key.
Manufacture – A watchmaking company that produces at least one of its own movements.
Marine chronometer – A highly accurate mechanical or electronic timekeeper that is enclosed in a box and is used for determining the longitude on board a ship. Marine chronometers with mechanical movements are mounted on gimbals so they are in the horizontal position that is essential for their precision. The first recorded Marine Chronometer is the Harrison H1.
Measurement conversion – A feature that allows the wearer to convert one type of measurement into another. It usually consists of a graduated scale on the bezel or dial.
Mechanical watch movement – This is the traditional watch movement. A mechanical watch is driven by a slow release of power from a mainspring via a set of small cog wheels. The spring can be wound up manually or kinetically using automatic systems.
Minute repeater – A function on a watch that sounds the time in hours, quarters or minutes.
Moonphase – A window in a watch which indicates the phases of the moon through 29 ½ days. Some moonphase watches incorporate a correction for the extra 44 minutes per month.
Movement – The motor of a watch that makes it keep time and perform functions.
Multi-functional – A watch that can perform other functions while keeping time.
Perlage – A design of circles applied to a watch movement.
Perpetual calendar – A watch that automatically considers variations in the length of the month and leap years and alters the calendar accordingly.
Pilots watch – An iconic watch archetype used by pilots and frequent travellers. The key features you can find are a high level of accuracy to coordinate take-off and landing timetables, an altimeter to measure how high you are flying and multiple time zone functions to account for world travel.
Pin buckle – A pin buckle is a common fastening system found on watch straps. One side of the strap is passed through the buckle which is held in place by a pin.
Power reserve indicator – A feature of some mechanical watches which indicates how much longer the watch will operate before it needs to be wound again. It is also known as the reserve de marche.
Pulsimeter – A feature on chronograph watches that allow it to measure pulse rate. They were originally designed for doctors.
Push-piece – A button designed to activate a function such as alarm or timer.
PVD – PVD stands for physical vapour deposition, which is a method of coating an entire watch and bracelet in a thin layer of titaniumnitrade, a super durable material that helps protect the watch from scratches.
Quartz crystal – The slice of synthetic quartz crystal within a quartz movement watch. When an electric current is passed through the quartz it oscillates. It oscillates at the rate of 32.768 hertz, dividing time into equal segments and therefore regulating the time.
Quartz movement – This is an electronic watch movement with a quartz crystal that oscillates when a current is applied to it. The power to run the watch is normally provided by a battery or a capacitor. A quartz movement is generally more accurate than a mechanical movement.
Radio controlled – Radio Controlled watches receive radio signals that allow them to adjust themselves to the correct time according to an atomic clock.
Rattrapante – See. Flyback hand. A feature on some chronographs to time races.
Retrograde – A hand that travels along a linear track and upon reaching the end jumps back to the beginning.
Regulation – A process of calculating a watch’s accuracy in various conditions such as orientation and temperature. A watch that succeeds rigorous regulation is called a chronometer.
Regulator – A regulator what shows hours and minutes on separate dials, or sub dials. Historically used as a master clock in which to set other watches/clocks against.
Roman numerals – I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII are Roman numerals used in place of Arabic numerals or indices.
Rotating bezel – A bezel that rotates.
Rotor – This is the oscillating part of an automatic watch that winds the mainspring.
Sandblasting – Sometimes referred to as beadblasting, sandblasting is a method of finishing a metal by cleaning and removing imperfections from the surface of the metal by firing sand or small beads at it with high velocity.
Sandwich dial – Sandwich dials are made of two pieces sandwiched together. The bottom piece is coated in lume and the top piece has indices or numerals carved into it to allow the lume to shine through.
Sapphire crystal – A crystal, the cover that protects the watch face, made of synthetic sapphire – a transparent, scratch resistant substance.
Screw down crown – A crown which screws down into a threaded barrel to aid a watch’s water resistance.
Shock absorber – A resilient bearing which takes up the shocks received by the watch’s balance staff and protects its pivots from damage.
Skeletonisation – A watch where the dial has been removed allowing full or partial visibility of the watch’s movement.
Slide rule – A device consisting of a scale on the outer edge of a watch face which enables mathematical calculations.
Solar powered batteries – Batteries in a quartz watch that are recharged via solar panels on the watch face.
Splits seconds hand – This refers to two hands – a flyback (rattrapante) hand and a regular chronograph hand. Both hands move together but, to time laps or finishing times, the wearer can stop the flyback hand while the chronograph hand continues. This, in effect, splits the hand in two.
Stopwatch – A watch with a seconds hand that measures intervals of time. When a stopwatch is incorporated into a watch, both the stopwatch and the standard watch are called a chronograph.
Stepping motor – The part of a quartz analogue movement that moves the gear train and in turn moves the watch’s hands.
Subsidiary dial (Sub-dial) – A small dial on a watch face used for purposes such as indicating the date or keeping track of elapsed time.
Sunray – Sunray is a pattern of lines intersecting at a central point, like the rays of the sun. It is typically achieved using a brushing technique.
Swiss-made – A watch can only be said to be Swiss-made if 60% of it was assembled, started, adjusted and controlled by the manufacturer in Switzerland.
Swiss A.O.S.C – A certificate of origin, a mark that identifies that a watch has been assembled in Switzerland and has components of Swiss origin.
Tachymeter – A set of markings on the outside of a watch which measures the wearer’s speed over a known distance. This is used in conjunction with the seconds hand.
Telemeter – The telemeter is a scale on your watch that can be used to calculate the approximate distance between you and an object that can be seen or heard. It is often found on chronographs in conjunction with a tachymeter.
Thermally-blued – Thermally-blued metal has undergone a heating process which naturally changes the colour of the metal to a blue or purple tone.
Thirty minute recorder – A subsidiary dial on a chronograph that can time periods of up to 30 minutes.
Timer – A device for registering intervals of time without any indication of the time of day.
Tonneau – A tonneau watch is shaped like a barrel with two convex sides.
Totaliser – A mechanism that keeps track of and displays elapsed time, often on a subsidiary dial.
Tourbillon – A tourbillon is found in mechanical watches and is a device that eliminates timekeeping errors caused by the small differences in the rates a watch runs in the vertical and horizontal positions. It consists of a round cage, holding the balance and escapement. It rotates continuously at the rate of one rotation per minute.
Tritium – A luminescent substance that doesn’t require exposure to light to glow. Its radioactive properties make it controversial in consumer watches. Sometimes called H3 gas.
Unidirectional rotation bezel – A bezel that can be rotated in one direction only and is used to monitor elapsed time. A ratchet mechanism is often in place to prevent it rotating in the other direction. It is often found on divers watches to prevent the diver from running out of air by overestimating remaining air supply if the bezel is accidentally knocked off its position. The fact the bezel moves in one direction only means the diver can only underestimate remaining air supply.
Vibration – This refers to the movement of an oscillating element that is limited by two extreme positions. The balance of a mechanical watch usually vibrates at a rate of five or six a second.
Water resistance – the ability of a watch to withstand water to various pressures, measured in bar
Winding – This is the action of tightening the mainspring of a watch. It can be done manually, by means of the crown, or automatically, via a rotor which is made to swing by the movement of the wearer’s wrist.
Winding stem – Connects the crown to the movement.
World time dial – A dial that tells the time of up to 24 time zones around the world. The names of the cities are printed on the dial. The hour in a particular zone can be read by looking at the scale next to the city that the hour hand is pointing to. The minutes are read in the normal way. The dial is usually found on the outer edge of the watch face. Watches with this function are called world timers.
Yacht timer – A countdown time which shows or sounds warning signals during the countdown to a boat race. It is also called a regatta timer.
