Here's why:

* Disturbance: A wave is initiated by a disturbance, which is a change in the medium's state.

* Medium: The disturbance travels through a medium, which can be solid, liquid, or gas.

* Evenly Timed: The key is that these disturbances occur at regular intervals. This creates a repeating pattern of energy transfer through the medium.

Types of Waves:

* Transverse Wave: The disturbance moves perpendicular to the direction the wave travels (e.g., a wave on a string).

* Longitudinal Wave: The disturbance moves parallel to the direction the wave travels (e.g., sound waves).

Examples:

* Sound Waves: Created by vibrations in the air (a medium)

* Water Waves: Created by disturbances on the surface of water

* Light Waves: Electromagnetic waves that don't require a medium to travel