m = ( m 1 , m 2 , m 3 ) is conventionally written as ( h , k , ℓ ℓ ) or ( h k ℓ ℓ ) , called Miller indices ; m 1 is replaced with h , m 2 replaced with k , and m 3 replaced with ℓ ℓ . Each lattice point ( h k ℓ ℓ ) in the reciprocal lattice corresponds to a set of lattice planes ( h k ℓ ℓ ) in the real space lattice. (A lattice plane is a plane crossing lattice points.) The direction of the reciprocal lattice vector corresponds to the normal to the real space planes. The magnitude of the reciprocal lattice vector K m is given in reciprocal length and is equal to the reciprocal of the interplanar spacing of the real space planes.