Balance Wheel - An oscillating wheel controlled by a spring. This wheel governs the accuracy of the watch by moving at a steady rate.

Band - The term used to refer to the strap which holds a watch to one's wrist. More specific terms include "Bracelet" (a flexible metal band) and "Strap" (a band made from a material other than metal).

Barrel - The cylindrical container which holds the mainspring of the watch and provides the power to the gear-train.

Caseback - The covering on the back of the watch.

Chronograph - The technical term for a stopwatch. Specifically a watch which measures a discrete duration, rather than reporting the current time of day.

Chronometer - A precision watch which has met stringent accuracy standards set by the C.O.S.C. in Switzerland. These watches have been tested in a variety of temperatures and positions and maintain consistent time.

Crown - The winding knob of the watch, used to wind the mainspring and set the hands.

Crystal - A piece of glass and clear plastic. This protects the dial and hands.

Escapement - A portion of the movement which regulates the release of energy from the mainspring. This is the part of the watch that enables it to "keep time" accurately.

Gear Train - A system of gears and pinion which transmit power from a mainspring to the escapement.

Hairspring - A thin, spiral-shaped spring which causes the balance wheel to oscilate and controls its motion. This spring is part of the fundamental timekeeping mechanism of the watch, and its design can severely affect the accuracy of the watch.

Jewel - Usually made of a synthetic gem such as ruby or sapphire, this small concave cap is used as a bearing for a wheel pivot to help reduce friction. Generally speaking, a higher "jewel count" indicates a higher quality watch. 19-jewel or higher is typically considered a high grade of watch.

Movement - The inner works of the watch. Contained within the "case".

Tourbillon - A system designed to reduce the timing errors caused by gravity.The system suspends the escapement on a rotating axis which regularly rotates over a set time period.