The question separates two related but distinct ideas about sound: the physical property of the wave itself, and the sensation that this property creates inside the brain.

Every sound is a longitudinal wave, and one of its measurable physical quantities is frequency, the number of complete vibrations that pass a point each second, measured in hertz (Hz).

When these vibrations reach the ear, they are converted into nerve signals; the brain then interprets the frequency and produces a perceived sensation of how 'high' or 'low' the sound is. That perception is called pitch.

The relationship is direct: a high-frequency wave (for example 4000 Hz) is heard as a high pitch, while a low-frequency wave (for example 100 Hz) is heard as a low pitch.

Frequency is the physical measurement in hertz, not the perception, so it is not the term for the brain's interpretation. Wavelength is the spatial distance between two successive crests of the wave, again a physical quantity, not a sensation.

Tone (or timbre) describes the quality of a sound that lets us tell a violin from a flute even at the same pitch; it depends on the mix of overtones, not on a single frequency, so it does not answer the question either.

Hence the perceptual term the brain uses to interpret the frequency of a sound is Pitch.