wavelength (transverse wave) – the distance from one crest to the next crest or the distance from one trough to the next trough

Note: Transverse wave think rope moving up and down.

The definition of wavelength is self explanatory, it's the length of a single wave.

Wavelength is the distance between consecutive identical points on a transverse wave, such as from one peak (crest) to the next peak, or from one trough to the next trough. It is measured in metres and is represented by the Greek letter lambda (λ).

It is measured in metres and is represented by the Greek letter lambda (?).

Different types of transverse waves have difference wavelengths - for example, in the electromagnetic spectrum, radio waves have very long wavelengths (up to kilometres), while gamma rays have extremely short wavelengths (less than the size of an atom).