The amplitude is a characterizing deflection of an oscillation, the elongation. It is the deflection of a physical quantity, e.g. an electric voltage, from its rest position (0-point) to a positive or negative value.
Amplitude (a) is expressed in a physical quantity, for example, as voltage, current, temperature, loudness, etc., and has several criteria for evaluation such as peak amplitude, peak-to-peak amplitude, and others.
The specification of amplitude can be time-related, such as at a time "t", it can also refer to minimum or maximum values, such as peak amplitude or peak-to-peak amplitude.