Distance between corresponding points of two consecutive waves.
"Corresponding points" refers to two points or particles that have completed identical fractions of their periodic motion . In transverse waves, wavelength is measured from crest to crest or from trough to trough. In longitudinal waves, it is measured from compression to compression or from rarefaction to rarefaction. Wavelength, λ, is equal to the speed v of a wave in a medium divided by its frequency f , or λ = v / f .