Which wave characteristic indicates the distance between two adjacent troughs?

The distance between two adjacent troughs in a wave is defined as the wavelength. Wavelength is a fundamental characteristic of waves that quantifies the spatial period of the wave, or how far one complete cycle of the wave extends. In the context of a water wave, for instance, the distance from one trough to the next trough or from one peak to the next peak represents the wavelength.

Conversely, amplitude refers to the maximum displacement of the wave from its rest position, which does not measure distance between consecutive features of the wave. Frequency relates to how often a wave cycles in a given time frame, measured in hertz, and is not concerned with the spatial distance between wave components. The medium is the material through which the wave travels (such as air, water, or solids) but does not provide information about the measurements of wave characteristics like distance. Thus, recognizing that wavelength specifically refers to the distance between successive similar points of the wave makes it clear why it is the correct characteristic in this context.