Terminology
Horological Glossary
Every technical term has its own reference page with a short definition, a full explanation and cross-references to the mechanisms, movements and object types where it applies.
A
- AdjustedTrade
- A movement regulated for specified conditions, historically marked on the plate.
- Adjuster (watch adjuster)Trade
- A skilled worker responsible for regulating a movement's rate across positions and temperatures.
- Albert chainCollecting
- A watch chain worn across the waistcoat with a T-bar through a buttonhole.
- AmplitudeRegulation
- The angular swing of a balance wheel from rest to one extreme and back.
- Auction estimateCollecting
- A pre-sale price range published by an auction house, not a guarantee of the eventual hammer price.
- Automatic winding (self-winding)Mechanism
- A mechanism using an oscillating or rotating weight to rewind the mainspring from wrist motion.
B
- BalanceRegulation
- The oscillating wheel that, with its spring, forms a watch's time base.
- Balance staffMechanism
- The pivoted axle carrying the balance wheel, hairspring collet and impulse or safety rollers.
- Banking pinsMechanism
- Two pins limiting the swing of the pallet fork to its correct engagement range.
- Barrel arborMechanism
- The central spindle of the mainspring barrel, hooked to the spring's inner coil.
- Beat errorRegulation
- Asymmetry between the two halves of a balance's vibration.
- Beat errorRegulation
- Unequal duration of the balance's two swings about its rest point.
- BezelCase & Dial
- The ring holding the crystal in place, sometimes hinged and sometimes fixed or screwed.
- Bimetallic balanceRegulation
- A split balance rim of two metals that changes shape with temperature to compensate the hairspring.
- BowCase & Dial
- The ring or loop at the top of a pocket watch case through which a chain or fob is attached.
- BowCase & Dial
- The ring at the top of a pocket-watch case through which a chain is passed.
- Box and papersCollecting
- The original packaging and documentation accompanying a watch at sale.
- Breguet handsCase & Dial
- Slender hands with a pierced eccentric circle near the tip.
- Breguet numeralsCase & Dial
- An openwork, slightly scrolled numeral style associated with Abraham-Louis Breguet's workshop.
- Breguet overcoilMechanism
- A raised, curved terminal curve on a flat hairspring that improves its concentric development.
- Breguet overcoilRegulation
- A hairspring whose outer turn is raised and curved over the body of the spring.
- BridgeMechanism
- An individual shaped plate, rather than a full upper plate, supporting one or more wheels.
C
- Calendar mechanismMechanism
- Dial-train gearing that advances a date, day or month indication once every twenty-four hours.
- Cannon pinionMechanism
- A friction-fitted pinion on the centre wheel arbor that carries the minute hand.
- Cannon pinionMechanism
- The friction-fitted pinion carrying the minute hand.
- Cap jewelMechanism
- A flat jewel closing the end of a pivot hole to control endshake and hold oil.
- Case numberCollecting
- A serial number stamped in the case, independent of the movement number.
- Centre wheelMechanism
- The train wheel, usually turning once per hour, that carries the minute hand via the cannon pinion.
- Champlevé enamelCase & Dial
- An enamelling technique in which recesses cut into a metal surface are filled with enamel and fired.
- ChatelaineCollecting
- A decorative clasp worn at the waist carrying a watch, key, seal and other implements.
- ChronographComplication
- A watch mechanism adding start, stop and reset timing functions to ordinary timekeeping.
- Chronometer escapement (detent)Mechanism
- A detached escapement giving direct, unbuffered impulse to the balance, used chiefly in marine chronometers.
- Click and ratchetMechanism
- The pawl-and-toothed-wheel assembly that prevents the mainspring from unwinding while being wound.
- Cloisonné enamelCase & Dial
- An enamelling technique using thin applied wires to separate colour fields before firing.
- Cock (balance cock)Mechanism
- A single-footed bridge, usually pierced and engraved, supporting the balance staff's upper pivot.
- Column wheelMechanism
- A vertical stepped wheel controlling the sequencing of chronograph functions.
- ComplicationTrade
- Any function added to a watch beyond basic timekeeping, such as striking, calendar or chronograph work.
- ComptoirTrade
- A Swiss trading house that commissioned, finished and exported watches under its own or a client's name.
- ConservationCollecting
- Stabilising an object and preventing further loss, in preference to renewing its material.
- Consular caseCase & Dial
- An early single case with a domed back and stepped bezel, transitional from pair cases.
- Côtes de GenèveCase & Dial
- Parallel striped decoration applied to bridges and plates in Swiss practice.
- Crown wheelMechanism
- The escape wheel of a verge escapement, with teeth projecting axially like a crown.
- CrystalCase & Dial
- The transparent cover over the dial, historically glass and later also acrylic and sapphire.
- CuvetteCase & Dial
- An inner dust cover hinged over the movement of a pocket watch.
- Cuvette (dust cover)Case & Dial
- An inner metal cover, hinged or snap-fitted, protecting the movement inside the case back.
- Cylinder escapementMechanism
- A frictional-rest escapement using a slotted cylinder on the balance staff.
D
- DamaskeeningCase & Dial
- Decorative machine-engraved patterning on American watch plates.
- DepthingMechanism
- How deeply a pinion and wheel, or pallet and escape tooth, engage each other.
- Dial trainMechanism
- Collective term for the motion works and any dial-side complications geared from it.
- Double-sunk dialCase & Dial
- An enamel dial with the chapter ring and sub-seconds recessed at different depths from the main surface.
- Double-sunk dialCase & Dial
- An enamel dial built in stepped levels, with the seconds and chapter areas recessed.
- Drop and lockRegulation
- Escapement measurements describing free travel before locking and depth of lock on the pallet.
- Duplex escapementMechanism
- A frictional-rest escapement with two sets of teeth on the escape wheel serving locking and impulse separately.
- Dust coverCase & Dial
- Any inner cover, of metal or later of celluloid or plastic, protecting the movement from dust ingress.
- Dust coverCase & Dial
- A thin cover protecting the movement from dust inside the case back.
- Dynamic poisingRegulation
- Poising performed while the balance is oscillating, correcting for hairspring as well as balance imbalance.
É
- ÉbaucheTrade
- An unfinished rough movement, complete in layout but lacking escapement finishing, jewelling, decoration or a signature.
- ÉtablissageTrade
- The distributed Swiss system of production in which specialist firms supply components later assembled and finished by others.
E
- Enamel (porcelain) dialCase & Dial
- A dial of vitreous enamel fired onto a metal base.
- Enamel dialCase & Dial
- A dial made by fusing powdered glass to a metal disc, giving a hard, glossy, light-fast surface.
- EndshakeRegulation
- The small permitted axial freedom of a wheel or balance between its bearings.
- Engine turning (guilloché)Case & Dial
- A mechanically engraved decorative pattern cut into a case or dial using a rose engine or straight-line lathe.
- Escape wheelMechanism
- The last wheel of the going train, which delivers impulse to the balance or pendulum via the escapement.
F
- FinisseurTrade
- A specialist workshop or worker who completed an ébauche to a saleable standard.
- Flyback (chronograph)Complication
- A chronograph function allowing the running seconds hand to reset and restart in a single action.
- FobCollecting
- A short ribbon or chain, or the ornament hung from it, carrying a watch in the pocket.
- FrankenwatchCollecting
- A watch assembled from parts of different origin and presented as original.
- FrankenwatchCollecting
- A watch assembled from parts of different watches and presented as original.
- Free-sprungRegulation
- A balance regulated by adjusting its own weights rather than by a hairspring index.
- FuseeMechanism
- A tapered grooved cone that equalises mainspring torque through a chain or gut line.
G
- Going barrelMechanism
- A mainspring barrel that drives the train directly, without a fusee.
- Going barrelMechanism
- A mainspring barrel whose toothed rim drives the train directly, without a fusee.
- Gold filledCase & Dial
- A case of base metal with a bonded layer of gold, often warranted for a stated number of years.
- Grading scaleCollecting
- Any of several inconsistent verbal or numeric scales used to describe condition.
- Grande sonnerieTrade
- A striking complication that sounds the hours and quarters automatically, unprompted, as they pass.
H
- Hairspring (balance spring)Regulation
- The fine spiral spring that returns the balance and sets the oscillation period.
- HallmarkCase & Dial
- An official assay mark certifying the precious-metal standard of a case.
- HallmarksCollecting
- Assay office marks certifying precious-metal content, often datable to a year.
I
- Import markCase & Dial
- An assay mark applied to foreign gold and silver cases on entry to a market.
- IsochronismRegulation
- The property of keeping the same rate regardless of amplitude or state of wind.
J
- Jewel countMechanism
- The number of jewelled bearings and functional jewels in a movement.
- JewelsMechanism
- Hard synthetic or natural stone bearings reducing pivot friction and wear.
- JobberTrade
- A wholesale dealer who bought movements, cases and dials separately and supplied assembled watches to retailers.
K
- KarruselComplication
- A rotating-carriage escapement mounting related to the tourbillon, developed as a cheaper alternative.
- Keyless worksMechanism
- The lever and clutch system allowing winding and hand-setting via the crown, without a key.
- Keyless worksMechanism
- The stem, crown and levers that allow winding and setting without a key.
L
- Lépine calibreMechanism
- A thin movement layout with separate bridges and the winding at twelve, in line with the seconds.
- Lever setCase & Dial
- A setting system requiring a small lever to be pulled before the hands can be moved.
- Lever setCase & Dial
- Setting arrangement in which a small lever under the bezel must be pulled out before the crown will set the hands.
- LugsCase & Dial
- Projections on a case that anchor the strap or bracelet, characteristic of wristwatches rather than pocket watches.
- Luminous paint (radium)Case & Dial
- Radioactive luminous compounds applied to dials and hands from the early twentieth century.
M
- MainspringMechanism
- The coiled spring that stores energy to drive the train.
- Maintaining powerMechanism
- A device that keeps the train running while a fusee or spring clock is being wound.
- Maltese crossMechanism
- The cross-shaped stopwork finger seen on high-grade Geneva barrels.
- Marriage (married watch)Collecting
- A watch assembled from a case and movement that did not originally belong together.
- Minute repeaterMechanism
- A repeater sounding hours, quarters and individual minutes.
- Montgomery dialCase & Dial
- A minute-marked dial numbered for every minute, associated with American railroad use.
- MoonphaseComplication
- A dial-train indication tracking the lunar synodic cycle, usually via a rotating disc.
- Motion workMechanism
- The wheels under the dial that reduce minute-hand rotation to hour-hand rotation.
- Motion worksMechanism
- The reduction gearing beneath the dial that drives the hour hand at one-twelfth the minute hand's speed.
- Movement numberCollecting
- The number engraved on the movement plate or bridge identifying that movement.
N
- Negative setMechanism
- A setting system that relies on the case to hold the movement's setting parts in the winding position.
O
- Original conditionCollecting
- The state of an object as it left the maker, with no later alteration, replacement or refinishing.
- Over-polishedCollecting
- A case that has been buffed heavily enough to round its edges, blur hallmarks or remove engine turning.
P
- Pair caseCase & Dial
- An inner case holding the movement within a separate outer protective case.
- Pallet forkMechanism
- The forked lever carrying two jewelled pallet stones that locks and unlocks the escape wheel.
- PatinaCollecting
- Surface change accumulated through age, handling and environmental exposure.
- PendantCase & Dial
- The stem and its case fitting, through which a pocket watch is suspended and wound.
- PendantCase & Dial
- The neck of a pocket-watch case carrying the crown and bow.
- Perpetual calendarComplication
- A calendar complication that automatically accounts for month lengths and leap years.
- Pillar plateMechanism
- The main lower plate of a movement, to which pillars, the barrel and the train are fitted.
- Pocket watch caseCase & Dial
- The protective housing, described by configuration, material and construction.
- Poise (static poising)Regulation
- The condition of a balance wheel whose centre of mass coincides with its pivot axis.
- PoisingRegulation
- Balancing a balance wheel so it has no heavy spot in any position.
- Positional errorRegulation
- Variation in rate depending on the orientation in which a watch is held or worn.
- Positional errorRegulation
- Rate variation between dial-up, dial-down and the vertical positions.
- Power reserve indicatorComplication
- A dial indication showing the remaining run of the mainspring before the watch stops.
- Private label (private brand)Trade
- A watch sold under a retailer's or distributor's name rather than the actual manufacturer's.
- ProvenanceCollecting
- The documented history of ownership and origin of an object.
R
- Rack and snailMechanism
- A striking-train mechanism that counts the hour by a rack falling against a stepped snail cam.
- Railroad dial (Montgomery dial)Case & Dial
- A dial style with bold, widely spaced Arabic numerals for both hour and minute tracks, aiding rapid reading.
- RateRegulation
- The daily or per-period gain or loss of a timekeeper relative to true time.
- Re-casedCollecting
- A movement housed in a case other than the one it left the factory in.
- Re-dialledCollecting
- A dial that has been refinished, repainted or reprinted rather than conserved.
- RedialCollecting
- A dial that has been repainted or refinished rather than surviving in its original printed or enamelled state.
- Regulator (index)Regulation
- A sliding lever that effectively lengthens or shortens the active portion of the hairspring to adjust rate.
- Regulator indexRegulation
- The lever carrying curb pins that alters the hairspring's working length.
- RemontoireMechanism
- A secondary spring or weight, rewound at intervals, that delivers uniform torque to the escapement.
- RepeaterMechanism
- A striking mechanism that sounds the time on demand.
- Replacement partsCollecting
- Non-original components fitted during a watch's working or restoration life.
- Retailer signatureTrade
- A name on the dial or movement identifying the seller rather than the manufacturer.
- Roller tableMechanism
- The disc on the balance staff carrying the impulse jewel that engages the pallet fork.
- RotorMechanism
- The oscillating weight of an automatic movement that rewinds the mainspring via a reduction and reversing gear train.
- Run to bankingRegulation
- The lever's remaining travel after unlocking, up to the banking limit.
S
- Safety rollerMechanism
- A disc on the balance staff, notched to work with a guard pin, preventing the pallet fork from moving out of position.
- SavonnetteCase & Dial
- A hunter-case layout with the winding crown at three relative to the dial.
- Sector (kite) dialCase & Dial
- A dial layout using shaped sectors, often an arrow or kite form, rather than a plain circle for subsidiary displays.
- Secular rateRegulation
- The gradual, long-term drift in a timekeeper's rate as its parts settle and lubricants age.
- Serial numberCollecting
- The factory number on a movement, used for dating and grade research.
- Service historyCollecting
- A documented record of repairs, parts replacement and maintenance performed on a timepiece.
- Spade handsCase & Dial
- Hands with a flat spade- or shovel-shaped terminal.
- StopworkMechanism
- A device limiting how far a mainspring may be wound or run down.
- Stopwork (Geneva stop)Mechanism
- A star-and-finger mechanism limiting the usable turns of the mainspring barrel.
- Sub-seconds dialCase & Dial
- A small subsidiary dial, usually at six o'clock, showing running seconds separately from the main hands.
T
- Temperature compensationRegulation
- Design features that reduce rate variation caused by thermal expansion and elastic modulus change.
- Timing machineRegulation
- A bench instrument that listens to a watch's escapement and displays rate, amplitude and beat error graphically.
- TourbillonComplication
- A rotating carriage for the escapement, intended to average out positional error caused by gravity.
- Train countMechanism
- The tooth and pinion counts that set a movement's beat rate.