What is the term for the distance from a wave's equilibrium to its crest or trough in a transverse wave?

The distance from a wave's equilibrium to its crest (the highest point of the wave) or trough (the lowest point of the wave) is defined as amplitude. In a transverse wave, this measurement reflects the extent of displacement of the wave from its rest position, and it is a crucial parameter that indicates the energy of the wave—the greater the amplitude, the more energy the wave carries.

Wavelength, on the other hand, measures the distance between successive crests or troughs in a wave. Compression pertains to regions in longitudinal waves where particles are close together, while expansion refers to areas where particles are spread apart in a wave. These concepts relate to different types of wave movements, thus reinforcing that the correct term for the distance from equilibrium to crest or trough in a transverse wave is indeed amplitude.