The amplitude of a wave measures the maximum displacement or magnitude of the wave from its equilibrium or rest position. In simpler terms, it represents the height or magnitude of the wave.
For example, in a transverse wave, such as a water wave or a wave on a string, the amplitude refers to the maximum distance that the particles of the medium are displaced from their equilibrium position. It can be thought of as the height of the wave from the undisturbed position.
In a longitudinal wave, such as a sound wave, the amplitude corresponds to the maximum compression or rarefaction of the medium. It indicates the maximum displacement of the particles from their average position as the wave passes through the medium.
The amplitude of a wave is typically represented by the letter "A" and is measured in units of length, such as meters (m) or centimeters (cm). It is a fundamental parameter of a wave and directly influences other wave characteristics such as intensity, energy, and loudness (in the case of sound waves).