Space lattice is defined as an array of points arranged in regular periodic fashion in three dimensional space such that each point in the lattice has exactly identical surrounding. The points are called lattice points or lattice sites.

A crystal structure is a space lattice in which the lattice sites are occupied by atoms or clusters of atoms. Each lattice point is associated with the same unit of groups of atoms, called the basis. The basis must be identical in composition, arrangement and orientation such that the crystal appears exactly the same at one point as it does at other equivalent points. When the basis is associated with each lattice site, the crystal structure is obtained.

Thus Space lattice + Basis = Crystal structure.