A wave is a disturbance that propagates through space or through a medium, carrying energy and information without requiring matter to travel with the disturbance over the same distance.

Disturbance and propagation

Imagine shaking one end of a stretched rope. A pulse travels along the rope even though each small piece of rope only moves around its local position.

The moving pattern is the wave; the material of the rope is the medium.

Waves with and without a material medium

Mechanical waves, such as sound or waves on a string, require matter that can be displaced and restored.

Electromagnetic waves can propagate through vacuum and do not require a material medium.

Pulses and periodic waves

A single localized disturbance is a pulse. If the source repeats its motion, it can produce a periodic wave with a repeating spatial and temporal pattern.

Superposition

When waves overlap, their disturbances can combine. This principle leads to interference, standing waves and many other characteristic wave phenomena.

The central idea is propagation: a local disturbance influences neighboring regions so that a pattern moves through space while the underlying system responds locally.