* Mechanical waves require a medium: Mechanical waves need a physical medium (like air, water, or a solid) to travel. They are vibrations or disturbances that propagate through the medium.

* X-rays are electromagnetic waves: X-rays are a form of electromagnetic radiation, which means they are composed of oscillating electric and magnetic fields. They do not require a medium to travel and can move through the vacuum of space.

Key Differences:

* Nature of the wave: Mechanical waves are disturbances in matter, while electromagnetic waves are disturbances in electric and magnetic fields.

* Medium: Mechanical waves need a medium, while electromagnetic waves do not.

* Speed: The speed of mechanical waves depends on the properties of the medium, while the speed of light (including X-rays) in a vacuum is a constant.

In summary: X-rays are not mechanical waves but are part of the electromagnetic spectrum, which includes visible light, radio waves, microwaves, and others.