The earliest timepieces date back to 3500 BC. The "shadow clock" or "gnomon" consisted of an obelisk or vertical stick that cast moving shadows. The ancient Egyptians were the first to divide a day into segments by the light of these markers. In the 14th century, large, mechanical clocks driven by heavy weights began to appear in bell towers. As these clocks featured only one hand, they were not very accurate.

The invention of the mainspring enabled the birth of the portable timepiece. In 1510, Peter Henlein designed a large, cylindrical pocket watch, which changed the face and size of tracking time. With the discovery of the pendulum in 1656 by Christian Huygens and later of the balance wheel, timekeeping became increasingly accurate. Since then, timepiece technology has greatly advanced from the primitive pendulum to the most accurate cesium clock.

An automatic or "self-winding" watch is a mechanical watch that winds itself automatically when worn. A wearer's everyday movement causes the rotor, a metal weight attached to the winding mechanism, to swing back and forth on its axis. The rotor's movement winds the mainspring, a flat, coiled spring, to drive the watch's mechanism.

Hand-wound clocks and watches run on mechanical movements. Developed in the 14th century, "mechanicals" contain a mainspring to drive the watch's mechanism. Part of this mechanism includes a pendulum or oscillating balance wheel with a hairspring that controls the rate at which the mechanism moves. In a mechanical watch, the wearer usually winds the mainspring once a day by turning the crown on the outside of the watch's casing. Mechanical clocks are usually wound with a winged key about once a week and many boast a strike or chime feature.

"Chronographs" are typically sporty watches with the ability to measure continuous or discontinuous intervals of time. These stopwatch functions may include measuring the speed, distance, and time of more than one event simultaneously. Not just for athletes, chronographs cater to any active lifestyle.

Most contemporary watches and clocks feature quartz movement. This technology allows an electric current to pass through a quartz crystal that creates constant oscillations resulting in very accurate timekeeping. A small battery supplies the power for a running time of two to five years.

Applied Numerals

Raised metal numbers attached to a dial on a timepiece.

Arbor

An axle that usually has a toothed wheel attached to it.

Auxiliary Dial

A small dial on a timepiece that shows additional information.

Balance

The oscillator that regulates or governs the speed of the movement.

Beat

The vibration or half oscillation of a movement.

Bezel

Metal plates that hold pivots or jewels in place in the movement on a timepiece.

Bubble Back

Term used for mechanical watches that have a deep, curved back.

Cabochon

Decorative stone set in the winding crown.

Calibre

A measurement used to denote the size of a movement in lines (2.256 mm) on a timepiece.

Chapter Ring

Circles denoting the hour, and sometimes minute, numbers or marks on a timepiece.

Complication

Mechanical watches with added functions including an alarm, perpetual calendar, power reserve indicator, split seconds or moon phase calendar.

Crown

The knob on a watch used for winding and setting the time and date.

Crystal

The cover made of glass, plastic, or synthetic sapphire that is fitted with a bezel on a watch.

Escape Wheel

Last wheel in going train, working with a pallet fork to control rate on a timepiece.

Escapement

Parts of the movement that allow the power of the mainspring of a mechanical movement to "escape" converting the rotary motion of gear train into precise 'to-and-fro' motion in a timepiece.

Frame

Plates and pillars in movement.

Frequency

The vibrations per hour of mechanical watches (VpH) or oscillations per second (Hz) of quartz pieces.

Hairspring or Balance Spring

Spiral spring attached to the arbor of balance to control oscillations in a timepiece.

Hertz (Hz)

The number of oscillations per second of electronic watches.

Horology

The art and science of timekeeping.

LCD

Continuous Liquid Crystal Display of numbers in a digital watch.

LED

Light Emitting Diode, a typically red display of numbers in early digital quartz watches.

Lug

Parts of the case to which the bracelet or strap is attached on a watch. Also known as horns.

Mainspring

A flat spring coiled in the barrel, which provides the power to drive the gear mechanism of a mechanical watch.

Motion Work

Gear train for driving the hour hand from the minute wheel on a timepiece.

Movement

Complete mechanism of a watch.

Oscillation

The back and forth regular movement, such as a balance wheel or pendulum, between two given points.

Pallet

Small part of the escapement of a mechanical watch that meets with the teeth of the escape wheel to relay an impulse to the balance.

Period

The duration of an oscillation. One swing of the balance in each direction.

Perpetual Calendar

A calendar mechanism that corrects itself for long and short months and leap years.

Pillars

Posts between the plates in the movement on a timepiece.

Pinion

Small-toothed wheel.

Pivot

The fine ends of the arbor, mounted in jewels or plates on a timepiece.

Rattrapante

A split-second function with flyback hands on a timepiece.

Retrograde

The swift return of hands on a watch to their starting point once they have spanned an arc completely.

Rotor

Pivoted weight in an automatic watch that winds the mainspring, using energy from the wearer's movement.

Screw-down Crown

A threaded winding crown on a timepiece, which screws tightly to the case to enhance water and dust resistance.

Skeleton Watch

A watch that has had most parts of the dial except the chapter ring removed to reveal the mechanism underneath and often has a crystal case back.

Tachymeter (Tachometer)

A measuring mechanism that can be used to calculate speed in miles or kilometres per hour.

Tourbillon

A mobile cage that holds the escapement of a mechanical watch movement and revolves, usually every 60 seconds, to overcome the effect of gravity on the running of a watch.

Train

Wheels and pinions that transmit power from the mainspring to the hands on a timepiece.

Tritium

Luminous paint that is very slightly radioactive, which is featured on timepiece dials, numbers and hands.

Vibration

A half oscillation, a swing from one side to the other without returning to the original position. It is the measure of the frequency of mechanical watches (VpH).