Which of the following components does a wave diagram typically represent?

A wave diagram primarily represents the characteristics of waves, which include wavelength and amplitude. Wavelength is the distance between successive crests or troughs of the wave, indicating how long one cycle of the wave is. Amplitude, on the other hand, measures the height of the wave from the rest position to the crest or trough. These two components are fundamental in defining the behavior and properties of waves, such as their energy and frequency.

In contrast, the other options represent different physical quantities that are not typically depicted in a wave diagram. Temperature and pressure pertain to thermodynamics, density and volume relate to matter properties, and velocity and mass involve classical mechanics. These concepts do not specifically describe the nature of wave motion, making them irrelevant in the context of wave diagrams.