the largest deflection from zero value of a quantity performing harmonic oscillations—for example, the swing of a pendulum from the equilibrium point or the deflection of the values of current intensity and voltage in an alternating electric current. In other words, oscillating amplitude indicates the range of the oscillations.
The oscillating quantity reaches its amplitude, or highest value, only once during each semiperiod. In harmonic oscillations the amplitude is a constant quantity. However, the term oscillating amplitude is often used in a broader sense, to refer to a quantity oscillating according to a rule more or less close to harmonic and sometimes even in references to oscillations which are far from harmonic.