Wavelength is defined as the:

Wavelength refers to the physical distance between consecutive peaks (or troughs) of a waveform, which is a fundamental concept in the study of waves, including sound and electromagnetic radiation. When discussing wavelengths, one typically measures the distance from one peak to the next in a repeating wave pattern. This measurement is crucial because it directly influences the wave's characteristics, such as its frequency and energy.

In the context of this question, the definition aligns with standard physics terminology, highlighting how wavelength is essential for understanding various phenomena in waves. The other options do not capture the full or accurate meaning of wavelength; for example, while the height of a waveform might be relevant to amplitude, it does not relate to wavelength. Similarly, discussing the length of the entire waveform or the distance between valleys does not provide the precise measurement that defines wavelength.