AUTOMATIC A mechanical watch movement, which is wound automatically by a pendulum swung by the physical motion of the wearer's wrist.
BEZEL The ring surrounding a watch's dial, typically with markings to indicate time zones, elapsed time or various other functions.
CALIBRE The model name of a watch's movement (similar to a car's engine code). It could be a number or a word, and varies by brand.
CHRONOGRAPH A watch that also includes stopwatch functions, to split time into intervals. Not to be confused with a chronometer (below).
CHRONOMETER A watch that has been officially tested at Contrôle Officiel Suisse des Chronomètres (COSC) to ensure its accuracy.
COMPLICATION Any function found on a watch beyond telling the hours, minutes and seconds (e.g. date, time zones, chronograph).
DIVING WATCH A watch designed to survive long periods underwater, while also indicating elapsed or remaining time to tell divers how much of their air supply remains.
ESCAPEMENT The ‘ticking' part of a mechanical watch that controls the energy released through the mainspring, and transfers it to the geartrain.
FLYBACK A type of chronograph that instantly restarts timing - zeroing the hands - when the wearer pushes a single button.
GMT A watch able to show time in two or more time zones (not just Greenwich Mean Time, as the name might suggest).
LUME Short for luminescent. Hands, numerals and markers may be coated with a lume material so that they glow in the dark.
MAINSPRING A spiral spring of metal, housed in the barrel, which - when wound -provides the source of power - or ‘fuel' - for a mechanical watch.
MANUAL WINDING A mechanical watch that must be wound by hand via the crown (usually found at the 3 o'clock position), typically once a day.
MANUFACTURE Always pronounced with comedy French accent: a watchmaker that builds its own movements.
MOON PHASE Device that shows the phases of the Moon via a subdial on a watch face. Realistically only of real use to sailors and werewolves.
MOVEMENT The ‘engine' of a watch. This could be mechanical or battery-powered, or a combination of both . If it's mechanical and automatic, it will be made up of the mainspring, barrel, geartrain, rotor, jewels, balance wheel and the escapement.
NOVELTY Swiss abuse of English, meaning ‘a brand-new model', though often they turn out to be novelties in the traditional sense...
PERPETUAL CALENDAR A function that shows the day of the week, date and month. Even compensates for leap years.
PILOT'S WATCH Usually oversized and designed for maximum legibility in the cockpit. Often features a GMT function and chronograph.
POWER RESERVE The amount of time for which a mechanical watch will run before it needs rewinding. Sometimes indicated on the dial, like a car's fuel gauge.
QUARTZ A type of movement in which power - from a battery - is passed over a sliver of quartz crystal, which vibrates at a certain frequency. A computer divides this into minutes and seconds. The pulses also power the hands or an LCD display.
REPEATER A watch able to indicate the time via chimes, the most desirable being minute repeaters - originally developed so you can tell the time in complete darkness.
SAPPHIRE CRYSTAL The transparent cover of a watch face. Protects the dial and hands and, depending on quality, is highly scratch- and shatter-resistant. May also include a ‘cyclops' window to magnify the date display.
TOURBILLON A type of mechanical watch movement that counteracts the effects of gravity and other forces that affect accuracy.
WORLD TIMER Like a GMT function, but able to show all 24 of the world's standard time zones, often with names of cities from each zone featured.