The cohomological Brauer group of a quasi-compact scheme "X" is defined to be the torsion subgroup of the étale cohomology group "H"2("X", Gm). (The whole group "H"2("X", Gm) need not be torsion, although it is torsion for regular schemes "X".) The Brauer group is always a subgroup of the cohomological Brauer group. Gabber showed that the Brauer group is equal to the cohomological Brauer group for any scheme with an ample line bundle (for example, any quasi-projective scheme over a commutative ring).