Working on content for the fall semester. When it comes to mechanical waves, the general consensus is there are at least two important types based on disturbance vs propagation directions: transverse and longitudinal. Some sources mention "surface waves" but this seems to me to be a combination of transverse and longitudinal and not a distinct type.
Another: a torsional wave seems to me to be a distinct type.
I've also seen the term axial wave. Is that yet another type or not?