The terminology behind watches is almost as complicated as the mechanics that drive them. The following terms serve as Watch Education 101 and features a list of many of the basic terms relating to the parts of a watch.

This simple glossary will help cut the confusion — consider this your reference point.

Automatic:

A mechanical watch that is wound by the motion of the wearer’s wrist rather than by twisting the crown. The motion of the wrist moves a counterweight (called a rotor) that then powers the mainspring, which turns the watch’s gears.

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Omega Automatic movement

Balance Wheel:

A weighted wheel that oscillates at a constant rate moving the watch’s gears and allowing the hands to move forward

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Typical mechanical balance wheel

Bezel:

A metal ring that surrounds the watch crystal. Often bezels rotate on watches (usually on dive watches) and contain a scale for time or other measurements; some remain stationary or do not have a scale and are purely decorative.

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Case Back:

The reverse side of a watch case that can be removed to access the inside of the watch.

Chronometer:

A watch that has been independently tested by the Official Swiss Chronometer Testing Institute (COSC) over the course several days in six different positions at three different temperatures, while remaining accurate to within -4/+6 seconds per day for mechanical watches.

Complication:

An additional function of a watch that goes beyond telling the time, like a stopwatch (chronograph), calendar or a moonphase indicator. Complications require additional parts and make a watch more expensive and complex to build.

Crown

A small knob on the side of the watch case that can be used to adjust the time, date and wind the watch to keep it running.

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Crystal:

The clear protective cover that covers the watch face, made from either synthetic sapphire, acrylic or glass. Synthetic sapphire is the most expensive to produce, though it is considerably more scratch resistant than either acrylic or glass crystals.

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Sapphire Crystal

Dial:

Also called the face, the dial displays the time and features numerals and markings as well as the hands.

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Escapement:

An internal component in a mechanical watch that transfers the power from a wound-up watch into the movement of the watch’s seconds hand by driving the balance wheel. This component is responsible for a watch’s ticking noise.

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balance wheel, pallet and escape wheel
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pallet and escape wheel

Exhibition Case Back:

Also called an “open” case back, this is a transparent cover on the backside of a watch case that shows off the inner workings of the movement.

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Frequency:

The speed at which a watch ticks (or beats), measured in either vibrations per hour or hertz. Most modern, high-end mechanical watches beat at a frequency of 28,800 VpH (4Hz). Watches that beat at 36,000 or higher are considered to be high-beat watches. A watch’s frequency is controlled by the oscillations of its balance wheel.

Flyback Chronograph:

A type of chronograph that can be reset without stopping the chronograph function (which is necessary in a normal chronograph). It’s particularly useful among pilots and other users who need to record multiple times in quick succession.

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Gear Train:

A system of gears that transfers power from the mainspring to the escapement.

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Hacking Seconds:

Also called “stop seconds,” this function will stop the seconds hand when the crown is pulled out. This makes it easier to synchronize a watch with another timepiece.

Indices:

The markings on the dial of a watch used to represent the hours in place of numerals.

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Jewels:

Synthetic rubies (sometimes synthetic sapphires) used as bearings at the heaviest points of wear in a watch movement in order to reduce friction between moving parts and increase a movement’s lifespan. Jewels have a naturally slicker surface than metal.  Jewels are only used to increase the accuracy of the movement and are not for decoration.

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Balance jewels and shock spring

Lugs:

The protruding pieces of metal at the top and bottom of a watch case where the strap is attached. The two ends of the lug hold a spring bar, which holds the strap in place.

Luminescence:

luminescence is the glow given off by watch numerals, indices and hands that have been coated with a photoluminescent material (“lumed”). While early watches used radioactive radium to create lume, most modern watches use non-radioactive phosphorescent substances like strontium aluminate.

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typical luminous watch hands

Mainspring:

A torsion spring that becomes tightened when a watch is wound, thus storing the energy of a watch. The force of the spring unwinding powers the watch. The mainspring is housed inside a small drum called a “barrel.”

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Automatic mainspring, and barrel

Movement:

The inner-working mechanism of a watch that can be either mechanical (automatic or hand-wound) or quartz (battery powered). Most watch manufacturers refer to their movements as “calibers.” In a mechanical movement, the main components are a mainspring, a gear train, an escapement and a balance wheel. In a quartz movement, the main components are a battery, a microchip circuit, a quartz crystal and a stepper motor.

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Quartz:

A quartz watch is a battery-powered watch. The battery sends an electric signal via a microchip circuit to a small quartz crystal that then vibrates at a precise rate. Those vibrations regulate a stepper motor that moves the watch hands. Quartz watches are considerably more accurate, more reliable and cheaper than their mechanical counterparts.

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Quartz watch movement

Small Seconds:

A small sub-dial separate from the main hour and minute function that displays the seconds.

Skeleton:

Similar to an exhibition case back, a skeleton watch shows off the inner workings of the watch, but does so through a transparent or partially cut-out dial so that the movement can be viewed from the front of the watch.

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Watch drawings

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