* Disturbance: A change or variation from a state of equilibrium. Think of a ripple in a pond or a sound wave traveling through the air.

* Medium: The substance or material that the disturbance travels through.

Here are some examples:

* Sound waves travel through air, water, solids, and even some liquids.

* Light waves can travel through a vacuum (like space), but also through transparent materials like glass or water.

* Seismic waves travel through the Earth's crust, mantle, and core.

* Water waves travel through water.

The type of medium affects how a disturbance travels. For example, sound travels faster through solids than through air, and light travels slower through water than through air.