Oscillation is a movement that starts from a dead center, goes in one direction, passes through the dead center again, goes in the opposite direction and ends when it returns to the dead centre.

In watchmaking we speak of the oscillation of the resonator which nowadays in a mechanical watch is a balance wheel, for an electronic watch a quartz, and for a wall clock a pendulum.

One oscillation corresponds to two vibrations. This is why what is counted with oscillations, such as hertz, which correspond to the number of oscillations per second, seems weaker than what is counted in vibrations.

The traditional frequency of a pocket watch corresponds to 2.5 hertz or 18,000 vibrations per hour and the second hand will jump 5 times per second.

The Swiss lever escapement in the pocket watch example above will therefore have a jump per vibration while the detent escapement has a jump per oscillation.