# Are ALL vibrations an exchange of kinetic and potential energy?

I'm taking a course on mechanical vibrational analysis and this is what I was told by my professor, but I'm curious if there are any counter-examples.

Consider a particle moving in an $|r|^2$ potential. One possibility is circular motion, which can be viewed as harmonic "vibrations" in orthogonal directions, $\pi /2$ out of phase. Now consider a particle moving in an $|r|^{-1}$ potential. Circular motion is also possible, but is it a "vibration"?