mechanical wave

Drop a pebble into a pond and ripples spread outward in rings, yet the water itself does not travel to the shore, a floating cork just bobs up and down in place. A mechanical wave is a disturbance that travels through a material (a medium), carrying energy from one place to another while the material itself only jiggles about where it started. The question it answers is: how can a sound or a ripple cross a whole room without any matter making the entire trip?

More precisely, a mechanical wave is a disturbance that propagates through a medium (a solid, liquid, or gas) by the medium's particles pushing and pulling on their neighbours. Each particle oscillates about its rest position, and the pattern of that oscillation moves forward at the wave speed v. The wave carries energy and momentum, but not the medium itself, so there is no net transport of matter. It requires a medium: no medium, no mechanical wave (a bell ringing in a vacuum makes no sound). The speed is set by the medium's stiffness and its inertia, for example on a string v = sqrt(T/mu), where T is the tension and mu is the mass per unit length.

Sound, ocean waves, waves on a rope, and seismic (earthquake) waves are all mechanical. An honest contrast: light and other electromagnetic waves are not mechanical, they carry energy through empty space and need no medium at all. So the word wave is a broader idea than the words mechanical wave.