Wavelength

The distance over-which a wave*’s shape repeats. For transverse wave*s, the wavelength is often drawn as a line from wave crest to wave crest, but it does not need to be. The wavelength is is the horizontal distance between successive crests, troughs or any other equivalent point between neighboring waves.

The fact that wavelength can be measured as the distance between any corresponding points on adjacent waves important for longitudinal wave*s, which lack crests and troughs. For these waves, wavelength can be shown as the distance between neighboring regions of compression.

As a distance, wavelengths are usually reported in meters with or without a prefix (kilo, micro, nano, etc).