A particle's Compton wavelength is a value used in calculation of Compton scattering and some other quantum-mechanical phenomena. It is also used as a general threshold regarding the size of interactions: that if the interaction involves distances less than the Compton wavelength, then quantum mechanical considerations are necessary in its analysis.
h λ = —— mc
It is directly related to the reciprocal of the particle's mass, the proportion being the quotient of the two physical constants, h/c, so it is effectively a type of measure of the particle's mass. Also, it is a lower bound on a particle's possible de Broglie wavelength, which additionally depends upon the particle's velocity. The above formula is the same as that of the de Broglie wavelength except using the speed of light, c rather than the particle's velocity, v.