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 is less than the Compton wavelength, then quantum mechanical considerations are necessary in its analysis.
h λ = —— mc
It is directly related to the inverse of the particle's mass, the proportion the quotient of the two physical constants, h/c, so it constitutes a type of measure of the particle's mass. Also, it is a lower bound on a particle's possible de Broglie wavelength, the latter of which depends upon the velocity as well as its mass. The above formula is like that of the de Broglie wavelength except with the speed of light, c rather than the particle's velocity, v.