oscillation

"Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes is used to be synonymous with "oscillation". Oscillations occur not only in physical systems but also in biological systems and in human society."


http://en.wikipedia.org/wiki/Oscillation

it just seemed appropriate right now and I can't even explain why.. some other time I'll come back to this and elaborate