The amplitude of a wave refers to the maximum displacement or intensity of the wave from its equilibrium position. In the case of a wave traveling through a medium, such as a water wave or a sound wave, the amplitude corresponds to the maximum height or displacement of the particles of the medium from their rest positions.
For example, in a water wave, the amplitude would be the maximum height of the water surface above or below its equilibrium level. In a sound wave, the amplitude corresponds to the maximum displacement of air particles from their average positions as the wave passes through.
In the context of electromagnetic waves, such as light waves, the amplitude refers to the maximum intensity or strength of the electric and magnetic fields comprising the wave. In this case, the amplitude does not correspond to a physical displacement, but rather to the magnitude of the electric and magnetic field components of the wave.
In summary, the amplitude of a wave represents the maximum displacement or intensity of the wave from its equilibrium position, whether it is a physical displacement in a medium or the strength of the electric and magnetic fields in the case of electromagnetic waves.