The material through which a wave travels is called the medium.

Here's why:

* Waves need a medium to travel: Most waves, like sound waves, need a medium to propagate. The particles in the medium vibrate and transfer energy, creating the wave.

* Examples of mediums: Air, water, solids, and even the ground are examples of mediums.

* Electromagnetic waves are an exception: Electromagnetic waves, like light and radio waves, can travel through a vacuum (empty space) because they don't require a medium to propagate.