What does the term 'wave' refer to in physics?

In physics, the term 'wave' specifically refers to a disturbance that travels through space and matter, transferring energy from one location to another without the physical transport of matter. When focusing on option C, it correctly identifies a key characteristic of waves: the distance between the crests of adjacent waves, known as wavelength. This measurement is crucial, as it helps determine the frequency and energy of the wave. For instance, in the context of sound waves, shorter wavelengths correspond to higher frequencies and, therefore, higher pitches. Understanding wavelength is fundamental to the study of various types of waves, including sound, light, and water waves.

The other options do not accurately define a wave. The amount of energy in a space relates to energy density rather than the definition of a wave itself. The distance between sound frequencies incorrectly implies a spatial measurement rather than focusing on the wavelength. The strength of a current in water pertains to fluid dynamics and is not related to the concept of wave formation or propagation in physics. Thus, the definition associated with wavelength is essential for understanding wave phenomena across different fields of physics.