Define the term Miller Indices.

Miller Indices are a process of explaining the orientation of a plane or set of planes into a lattice within relation to the unit cell. They were improved by William Hallowes Miller.

These indices are helpful in understanding several phenomena into materials science, as like describing the shapes of single crystals, the type of some materials' microstructure, the interpretation of X-ray diffraction patterns and the dislocation movement, that may find out the mechanical properties of the material.