Movement – the inner mechanism of a watch that keeps time and operates the watch’s functions.

Caliber – used to denote the size of a movement usually measured in lignes (2.256 mm); also used by manufacturers as “names’ for their movements.

Ligne – used to indicate the size of a mechanical movement, measured over the plate beneath the dial.  1 ligne = 2.256 mm (one twelfth of a “French inch”)

Ebauche – literally the basic frame; commonly used for an assembled movement, without escapement, balance and hairspring and mainspring.

Mainspring – a coiled flat spring which provides the power to drive the gear train of the mechanical watches.

Balance wheel – an oscillator, which regulates or governs the speed of the movement.  A flat ring which pivots on an axle.  It must be perfectly poised.  After it has swung one way, the spring at its center reverses it and makes it swing the other way – hence the “tick tock” of a mechanical watch.  Both balance and hairspring are made of a special alloy to offset the effect of temperature changes.
Hairspring or balance spring – a very delicate spiral spring attached to arbor of balance to control oscilliations.

Balance staff – the axle on which the balance pivots.

Jewels – used as bearings to reduce wear at points of greatest friction in movements.  Usually 17-21 jewels in mechanical watches.  By reducing friction they add years to a watch’s life.  Once they were natural rubies, but now are synthetic.  There design shape helps to hold oil at the specific point of lubrication.

Quartz crystal – an oscillator made of a tiny piece of synthetic quartz.  Its standard frequency is 32,768 times per second.

Hertz – Hz- the number of oscillations per second of electronic watches.