The distance from one crest to the next is known as what?

The distance from one crest to the next in a wave is referred to as the wavelength. Wavelength is a fundamental characteristic of a wave that describes the spatial period of the wave – in other words, it is the distance over which the wave's shape repeats. In graphical terms, it is the physical length between two successive crests (or troughs) in a wave, which helps to define how many cycles of the wave occur over a certain distance.

In contrast, other terms such as amplitude refer to the height of the wave from its rest position to its crest (or trough), frequency pertains to the number of cycles that occur in a given unit of time (usually per second), and period is the time it takes to complete one full cycle of the wave. Thus, the concept of wavelength specifically focuses on the measured distance between repeating points in the wave, making it distinct from these related terms.