ABSTRACT
P4.1. Oscillations ◮ General definitions. Oscillations are repetitive variations in the state of a system such that the state parameters vary in time according to a periodic or almost periodic law. If oscillations occur without external action due to system deviation from a stable equilibrium, the oscillations are said to be free or natural. If the oscillations occur under the action of an external periodic force, then they are said to be forced. The oscillations are characterized by their period T and frequency ν = 1/T (measured in hertzs: 1 Hz = 1 s-1). The term vibrations is often used in a narrower sense to mean mechanical oscillations, but sometimes is used synonymously with oscillations.
