Wavelength is a property of all waves. It is the distance between a point on one wave, and the same point on the next wave in the sequence.
It is shown in calculations as the lambda symbol (λ), and is defined as λ= Wavespeed/Frequency
Within the electromagnetic spectrum: radio waves have the longest wavelength but the lowest frequency; but gamma rays have the shortest wavelength and the highest frequency. All other electromagnetic waves are found between these two extremes of the spectrum.
Within Biomedical Sciences wavelength is usually referring to light, and is given the units of nanometres (nm). It is frequently used within spectrophotometry practicals, as certain proteins and compounds are identified by their absorbance of light at specific wavelengths.