dif·frac·tion 
(dĭ-frăkshən)
(dĭ-frăkshən)n.
Change in the directions and intensities of a group of waves after passing by an obstacle or through an aperture whose size is approximately the same as the wavelength of the waves.
[New Latin diffrāctiō, diffrāctiōn-, from Latin diffrāctus, past participle of diffringere : dis-, apart; see DIS- + frangere, to break; see bhreg- in the Appendix of Indo-European roots.]