The concept of a space lattice is fundamental in crystallography. A space lattice, or more simply a lattice, is an indefinitely extended regular array of points, in which the environment of each point is exactly the same. This implies that if the lattice is (1) translated parallel to itself, or (2) inverted about one of its points, or (3) rotated it will remain precisely the same as it was before such transformations. Such projective transformations as translation, inversion, or rotation are called symmetry operations. A lattice therefore may be said to be invariant in respect to certain specific symmetry operations. It is then said to possess certain symmetry elements.