Amplitude (of a symmetrical periodic quantity)
The maximum magnitude of a symmetrical periodic quantity within one period of the oscillation.
Note: 1 In German the term "amplitude" applies to the maximum instantaneous value of a sinusoidal oscillatory quantity. In the case of a non-sinusoidal quantity the term Scheitelwert is used.
Note: 2 Not to be confused with "Amplitude (of an observed heavenly body)" (1-2-125).
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)